国立感染症研究所

With the promotion of vaccination and natural infection, the proportion of immune carriers against the Omicron variant (BA.5 and BQ1.1) shows an increase in each age group, and it has been reported that the percentage is increasing particularly in the elderly population as a result of vaccination. However, immunity acquired both through vaccination and natural infection is considered to decrease over time, and it may have already declined in elderly people.

The nighttime population nationwide decreased during the year-end and New Year holidays, and then a continuous increasing trend has been seen in many regions.

Currently, the BA.5 lineage is the mainstream in Japan, but sublineages of the Omicron variant such as BQ.1 and XBB lineages, particularly XBB.1.5, which has been reported mainly in the US, are considered to have a higher possibility to escape the immune system, and have been pointed out to predominate among the increasing number of infected people overseas. Particularly regarding the BQ.1 lineage, the proportion is increasing domestically, and close attention is required. The proportion of BN.1.2 and BN.1.3 lineages, which are sublineages of the BA.2.75 lineage, has also increased in Japan.

With a full-fledged winter, temperatures are dropping nationwide, and ventilation may be difficult. Respiratory virus infections also tend to be prevalent in winter.

• As for the “vaccine for the Omicron variant," vaccination of all persons aged 12 and over who have completed the first vaccination should proceed.
• As both vaccines for the BA.1 and the BA.4 and BA.5 lineages are expected to be more effective than the previous vaccines, it is necessary to proceed with vaccination with the vaccine that can be given sooner. All eligible persons who wish to receive vaccination will be asked to receive the vaccine for the Omicron variant.
• Those who have not been vaccinated will be encouraged to consider getting the initial vaccination as soon as possible.
• Concerning children (ages 5 to 11), booster vaccinations will be promoted along with the initial vaccination. Concerning children (ages 6 months to 4 years), the initial vaccination will be promoted.
• It is necessary to promptly investigate how to use the novel coronavirus vaccine in the future.

• The national and local governments are required to secure a system that enables testing, and should further utilize testing.
• Perform frequent tests (approximately 2 or 3 times a week) of facility workers at facilities for elderly people.
• Establishment of a system for fever outpatients should be further promoted, so that patients with symptoms can self-test using an antigen qualitative test kit, and if the result is positive, they can promptly undergo health observation at a health follow-up center, etc.
• Further promotion of the utilization of antigen qualitative test kits, which have been switched to OTC and are sold on the internet.

• The status of COVID-19 in China is rapidly worsening, making it difficult to grasp the detailed situation. Based on this situation, temporary measures such as immigration inspections have been implemented since December 30, 2022 to avoid a sharp increase in the inflow of COVID-19 into Japan, and flexible responses will be taken while monitoring the infection situation in China.

In winter, it is also the time when the number of patients with diseases other than COVID-19 increases. With the support of the national government, prefectural governments must take measures mainly to avoid overcrowding of hospital beds and fever outpatient clinics as follows.

• Maintain the total number of beds required for patients infected with COVID-19 based on the bed securing plan, and promptly increase the number of beds in response to spreading of the infection. In addition, continue to increase the number of medical institutions that can handle COVID-19 by supporting improvement of the ability to treat COVID-19 cases, even at hospitals without any beds for infected patients (promotion of zoning of hospital rooms, etc.).
• In addition to immediate responses such as securing beds and developing temporary medical facilities that supplement hospital beds, efforts will be made to avoid being overwhelmed concerning the number of hospital beds and emergency medical care by using lodging facilities and resting beds, for example.
• Appropriate adjustment so that patients who need hospital treatment can be hospitalized preferentially (securing and expanding logistical support hospitals, and improving the hospital turnover rate, such as by dissemination of the standard for early discharge of 4 days, as a rule), implementation of frequent examinations at facilities for elderly people and others, and further strengthening medical support during normal times
• In addition to extending office hours and the number of outpatient clinics for fever patients, the outpatient medical care system is strengthened and prioritized by strengthening regional outpatient and testing centers and telephone and online clinics, etc.
• Local residents should be informed that they should refrain from visiting emergency outpatient units only to receive a precautionary examination if they do not have symptoms, for example, taking the actual situation in the region into consideration so that nobody is prevented from receiving treatment. To respond to concerns and questions when a patient’s physical condition deteriorates, the telephone consultation service by healthcare professionals should be thoroughly publicized, and this service should also be strengthened.
• Ensuring that test certificates are not required at workplaces and schools to start medical treatment.

• As measures for the possibility that there may be many patients with fever during simultaneous epidemics, the following efforts should be promoted according to the actual situation in each region: strengthening of the fever outpatient clinics, strengthening of telephone consultations and telemedicine in preparation for overcrowding of the fever outpatient clinics, expansion of health follow-up centers, securing of self-examination kits, strengthening of the consultation system, and prevention of overcrowded emergency medical care.
  The smooth supply of therapeutic drugs will also be promoted, including oral drugs that are new treatment options for COVID-19 and are prescribed after confirmation of the indication by a doctor. Pharmacies, etc. will be asked to use the consultation service of the Ministry of Health, Labour and Welfare when it is difficult to obtain antipyretic analgesics.
• The prefectures will work to strengthen and prioritize the health care system based on plans to establish systems such as strengthening of outpatient medical care systems in accordance with the actual conditions in each region.
• It is necessary to provide information and appropriate messages depending on the infection status to the public. In addition to calling for purchasing the antigen qualitative test kits and antipyretic analgesics as well as checking the contact information of consultation services, etc., persons at a low risk of severe symptoms will be encouraged to perform self-testing or to utilize their local health follow-up centers. While the emergency medical care system is usually overwhelmed in winter, people will be advised to do the following: check the “guide for ambulance services” in preparation for an acute illness or injury, consult a family doctor when hesitant to call an ambulance, use a telephone consultation service such as #7119, and call an ambulance without hesitation if necessary.
• At the same time, vaccination against COVID-19 and seasonal influenza should be promoted to those who are subject to vaccination.
• When the number of infected cases sharply increases and hospitals are overcrowded, measures depending on the situation are required, including requests/calls for residents and business operators to prevent spreading of the infection and to maintain the functions of the medical system, as well as highly effective measures to prevent the spread of infection including behavioral restrictions.

• It is necessary to promptly promote consideration of effective and appropriate surveillance to grasp the epidemic status. It is also necessary to continue monitoring of the trends of variants through genomic surveillance.
• Regarding the risk assessment of COVID-19, it is necessary to continue evaluation of the pathogenicity, infectivity, mutations, etc.

• It is necessary to publicize and recommend effective ventilation methods to prevent insufficient indoor ventilation (how to create airflow considering aerosols and installation of partitions that do not block the airflow, for example) due to the use of heating appliances due to low temperatures.

Re-inspection and implementation of the following basic infection control measures are needed.

• Continue proper wearing of nonwoven masks according to the situation, hand hygiene, thorough ventilation, etc.
• Avoid situations with a high risk of infection, such as the three Cs, congestion, and loud voices.
• In the event of a meeting at a restaurant, choose a venue certified by a third party, keep the number of people as small as possible, avoid loud voices and staying for a long time, and wear a mask when talking.
• People with symptoms such as sore throat, coughing, and fever should refrain from going out.
• Refer to the guidelines for hospital visits and the use of an ambulance.
• Prepare antigen qualitative test kits and antipyretic analgesics at home, and check the contact information of consultation services.
• To reduce the chances of contact as far as possible, it is necessary to take measures, such as promoting the use of telework again at the workplace.
• Organizers of events or meetings should fully evaluate the epidemic situation and risk of infection in the area, and consider whether or not to hold an event. If the event is held, measures should be taken to minimize the infection risk.
• Since the risk of infection remains during the shortened period of home care of those who test positive, they should monitor their own physical condition, such as measuring their own temperature, and taking thorough measures against infection when going out. They must also be asked to avoid contact with people who are at risk of aggravation, such as elderly people.
• To allow the minimum necessary outings, such as shopping for groceries, after 24 hours have passed since symptoms have subsided or when there are no symptoms, it is necessary to take voluntary actions to prevent infection, such as wearing a mask when going out or when having contact with people, keeping contact with people to a minimum period of time, and not using public transportation.

It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.

In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to the mucosa, aerosol inhalation, contact infection, etc.).

It has been shown that infection with the Omicron variant may present a relatively lower risk of hospitalization and aggravation than with the Delta variant. To evaluate COVID-19, including the Omicron variant, it is not only necessary to assess the severity as a disease but also of the transmissibility and the impact on the medical care system and society as a whole.

Concerning the death toll since the outbreak at the end of 2021, it is reported that the novel coronavirus is not the direct cause of death in quite a number of cases compared to the epidemic in the summer of 2021; for example, when elderly people who had been living in a facility for elderly people since before the infection were infected and died, the death was due to worsening of the underlying disease. There were many cases of serious respiratory failure due to typical viral pneumonia caused by the novel coronavirus infection from the beginning of the novel coronavirus outbreak until the outbreak of the Delta variant. However, during the Omicron variant outbreak, it was reported that other diseases than pneumonia became the main causes of death, such as exacerbation of the underlying disease that had been present before hospitalization and the onset of other complications during hospitalization.

Concerning the spread of infection last summer, there has been a continuing decrease in the rate of severe cases and increase in the ratio of elderly people among hospitalized patients as during the previous outbreak compared to spreading of the infection in the summer of 2021. Among the deaths during the 2022 summer outbreak, mechanical ventilation/nasal high flow use rates and steroid prescription rates were decreased compared to the 2021 outbreak.

Among the fatal cases of infected children who died of endogenous factors, there were some cases without any underlying diseases. The reports on the results of on-site investigations have stated that it is necessary to pay attention to neurological symptoms such as convulsions and disturbance of consciousness, and systemic symptoms such as vomiting and poor oral intake besides the respiratory symptoms.

Among the deaths that occurred at home in July and August last year, approximately 80% of the patients were 70 years and older, which is similar to the trend of all deaths during the same period. It suggests that there were also many deaths caused by other factors than COVID-19. In addition, according to the status of handling dead bodies known to be coronavirus positive, the number reported monthly has been the highest during the last December. The proportion of deaths due to coronavirus has recently reached approximately 30%. The local governments are developing treatment, testing and follow-up outpatient medical care systems including medical institutions. It is important to continuously endeavor to provide the necessary medical care to home care patients.

According to Japanese data, the risk of infection remains until 10 days after onset, and infectivity is high until 7 days after onset. Even after waiting for 5 days, a third of patients are still shedding infectious viruses. On Day 8 (after isolation for 7 days), most patients (approximately 85%) did not shed infectious viruses, and it was reported that even if patients did shed the virus, the amount of virus decreased to one-sixth that in the initial stage of onset after 7 days.

Concerning the conventional vaccine, the infection and disease onset prevention effects of the first vaccination against the Omicron variant are markedly reduced. The hospitalization-preventing effect is reported maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing, disease onset-preventing and hospitalization-preventing effects against infection with the Omicron variant, and information on how these vaccine effects are attenuated after a third vaccination has become available. Concerning the vaccine against the Omicron variant (BA.4-5), it has been reported that the preventive effect against disease onset was observed within 0 to 2 months (median 1 month) after vaccination.

While the BA.5 lineage continues to be mainstream in the world, there are many reports of sublineages of the Omicron variant and recombinants with characteristic mutations in the spike protein. There are also sublineages for which superiority in the increase in infected patients has been indicated, including the BQ.1 lineage (sublineages of the BA.5.3 lineage), as well as the XBB lineage (sublineages of the BJ.1 lineage [sublineage of the BA.2.10 lineage] and recombinants of the BM.1.1.1 lineage [sublineage of the BA.2.75.3 lineage]). In Europe, an increase in the proportion of the BQ.1 lineage has been confirmed, which is also increasing in Japan. In addition, the XBB.1.5 lineage (sublineages of the XBB lineage) is on an increasing trend in the US. The World Health Organization (WHO), etc., pointed out that the immune escape of these variants probably leads to dominance in the increasing number of infected cases, but the information obtained so far suggest that there is limited epidemiological and clinical knowledge of the infectivity and severity of the XBB.1.5 lineage. There are also no clear findings on the BN.1.2 and BN.1.3 lineages, which have been increasing in Japan. It is necessary to continue to collect data and analyze the situation and findings in other countries regarding these characteristics of the new sublineages and recombinants, and to continue monitoring by genome surveillance.

With the promotion of vaccination and natural infection, the proportion of immune carriers against the Omicron variant (BA.5 and BQ1.1) shows an increase in each age group, and it has been reported that the percentage is increasing particularly in the elderly population because of vaccination. However, immunity acquired both through vaccination and natural infection may decline over time.

As in previous years, the nighttime population decreased nationwide during the year-end and New Year holidays and then increased again.

Currently, the BA.5 lineage is the mainstream in Japan, but sublineages of the Omicron variant such as BQ.1 and XBB lineages, particularly XBB.1.5, which as been reported mainly in the US, are considered to have a higher possibility to escape the immune system, and have been pointed out to predominate among the increasing number of infected people overseas. Particularly regarding the BQ.1 lineage, the proportion is increasing domestically, and close attention is required. The proportion of BN.1.2 and BN.1.3 lineages, which are sublineages of the BA.2.75 lineage, has also increased in Japan.

With a full-fledged winter, temperatures are dropping nationwide, and ventilation may be difficult. Respiratory virus infections also tend to be prevalent in winter.

• As for the “vaccine for the Omicron variant," vaccination of all persons aged 12 and over who have completed the first vaccination should proceed.
• As both vaccines for the BA.1 and the BA.4 and BA.5 lineages are expected to be more effective than the previous vaccines, it is necessary to proceed with vaccination with the vaccine that can be given sooner. All eligible persons who wish to receive vaccination will be asked to receive the vaccine for the Omicron variant.
• Those who have not received vaccination will be encouraged to consider getting the initial vaccination as soon as possible.
• For children (ages 5 to 11), booster vaccinations will be promoted along with the initial vaccination. For children (ages 6 months to 4 years), initial vaccinations will be promoted.
• It is necessary to discuss promptly how to position the coronavirus vaccination in the future.

• The national and local governments are required to secure a system that enables testing, and should further utilize testing.
• Perform frequent tests (about 2 or 3 times a week for facility workers) for workers at facilities for elderly people.
• Establishment of a system for fever outpatients should be further promoted, so that patients with symptoms can self-test using an antigen qualitative test kit, and if the result is positive, they can promptly undergo health observation at a health follow-up center, etc.
• Further promotion of the utilization of antigen qualitative test kits, which have been switched to OTC and are sold on the internet.

• The status of the COVID-19 in China is rapidly worsening, making it difficult to grasp the detailed situation. Based on this situation, temporary measures such as immigration inspections have been implemented since December 30, 2022 to avoid a sharp increase in the inflow of the COVID-19 into Japan, and flexible responses will be taken while monitoring the infection situation in China.

In winter, it is also the time when the number of patients with diseases other than the COVID-19 increases. With the support of the national government, prefectural governments must take measures mainly to avoid overcrowding of hospital beds and fever outpatient clinics as follows.

• Maintain the total number of beds required for patients infected with the COVID-19 based on the bed securing plan, and promptly increase the number of beds in response to spreading of the infection. In addition, continue to increase the number of medical institutions that can handle COVID-19 by supporting improvement of the ability to treat COVID-19 cases, even at hospitals without any beds for infected patients (promotion of zoning of hospital rooms, etc.).
• In addition to facilitating the use of available hospital beds and developing temporary medical facilities to supplement hospital beds, making efforts to avoid a shortage of hospital beds and emergency medical care, such as utilization of lodging facilities and resting beds
• Appropriate adjustment so that patients who need hospital treatment can be hospitalized preferentially (securing and expanding logistical support hospitals, and improving the hospital turnover rate, such as by dissemination of the standard for early discharge of 4 days, as a rule), implementation of frequent examinations at facilities for elderly people and others, and further strengthening medical support during normal times
• In addition to extending the office hours and the number of outpatient clinics for fever patients, the outpatient medical care system is strengthened and prioritized by strengthening regional outpatient and testing centers and telephone and online clinics, etc.
• Local residents should be informed that they should refrain from visiting emergency outpatient units only to receive a precautionary examination if they do not have symptoms, for example, taking the actual situation in the region into consideration, so that nobody is prevented from receiving treatment. To respond to concerns and questions when a patient’s physical condition deteriorates, the telephone consultation service by healthcare professionals should be thoroughly publicized, and this service should also be strengthened.
• Ensuring that workplaces and schools do not require test certificates at the start of medical treatment.

• As measures for the possibility that there may be many patients with fever during simultaneous epidemics, the following efforts should be promoted according to the actual situation in each region: strengthening of the fever outpatient clinics, strengthening of telephone consultations and telemedicine in preparation for overcrowding of the fever outpatient clinics, expansion of health follow-up centers, securing of self-examination kits, strengthening of the consultation system, and prevention of overcrowded emergency medical care.

  The smooth supply of therapeutic drugs will also be promoted, including oral drugs that are new treatment options for COVID-19 and are prescribed after confirmation of the indication by a doctor. Pharmacies, etc. will be asked to use the consultation service of the Ministry of Health, Labour and Welfare when it is difficult to obtain antipyretic analgesics.

• The prefectures will work to strengthen and prioritize the health care system based on plans to establish systems such as strengthening of outpatient medical care systems in accordance with the actual conditions in each region.
• It is necessary to provide information and appropriate messages depending on the infection status to the public. In addition to calling for purchasing the antigen qualitative test kits and antipyretic analgesics as well as checking the contact information of consultation services, etc., persons at a low risk of severe symptoms will be encouraged to perform self-testing or to utilize their local health follow-up centers. While the emergency medical care system is usually overwhelmed in winter, people will be advised to do the following: check the “guide for ambulance services” in preparation for an acute illness or injury, consult a family doctor when hesitant to call an ambulance, use a telephone consultation service such as #7119, and call an ambulance without hesitation if necessary.
• At the same time, vaccination against COVID-19 and seasonal influenza of those who are subject to vaccination should be promoted.
• When the number of infected cases sharply increases and hospitals are overcrowded, measures depending on the situation are required, including requests/calls for residents and business operators to prevent spreading of the infection and to maintain the functions of the medical system, as well as highly effective measures to prevent the spread of infection including behavioral restrictions.

• It is necessary to promptly promote consideration of effective and appropriate surveillance to grasp the epidemic status. It is also necessary to continue monitoring of the trends of variants through genomic surveillance.
• Regarding the risk assessment of COVID-19, it is necessary to continue evaluation of the pathogenicity, infectivity, mutations, etc.

• It is necessary to publicize and recommend effective ventilation methods to prevent insufficient indoor ventilation (how to create airflow considering aerosols and install partitions that do not block airflow, for example) due to the use of heating appliances due to low temperatures.

Re-inspection and implementation of the following basic infection control measures are needed.

• Continue proper wearing of nonwoven masks according to the situation, hand hygiene, thorough ventilation, etc.
• Avoid situations with a high risk of infection, such as the three Cs, congestion, or loud voices.
• In the event of a meeting at a restaurant, choose a venue certified by a third party, keep the number of people as low as possible, avoid speaking in loud voices and staying for a long time, and wear a mask when talking.
• People with symptoms such as sore throat, cough, and fever should refrain from going out.
• Refer to guidelines for hospital visits and use of an ambulance.
• Prepare antigen qualitative test kits and antipyretic analgesics at home, and check the contact information of consultation services.
• To reduce the chances of contact as far as possible, it is necessary for measures at the workplace, such as again promoting the use of telework.
• Organizers of events or meetings should fully evaluate the epidemic situation and risk of infection in the area, and consider whether or not to hold the event. If the event is held, measures should be taken to minimize the infection risk.
• Since the risk of infection remains during the shortened period of home care of those who test positive, they should monitor their own physical condition, such as measuring their own temperature, and taking thorough measures against infection when going out. They must also be asked to avoid contact with people who are at risk of severe disease, such as elderly people.
• To allow the minimum necessary outings, such as shopping for groceries, after 24 hours have passed since symptoms have subsided or when there are no symptoms, it is necessary to take voluntary actions to prevent infection, such as wearing a mask when going out, keeping contact with other people at the minimum period of time necessary, and not using public transportation.

It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.

In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to the mucosa, aerosol inhalation, contact infection, etc.).

It has been shown that infection with the Omicron variant may present a relatively lower risk of hospitalization and aggravation than with the Delta variant. To evaluate COVID-19, including the Omicron variant, it is not only necessary to assess the severity as a disease but also of the transmissibility and the impact on the medical care system and society as a whole.

Concerning the death toll since the outbreak at the end of 2021, it is reported that the novel coronavirus is not the direct cause of death in quite a number of cases compared to the epidemic in the summer of 2021; for example, when elderly people who had been living in a facility for elderly people since before the infection were infected and died, the death was due to worsening of the underlying disease. There were many cases of serious respiratory failure due to typical viral pneumonia caused by the novel coronavirus infection from the beginning of the novel coronavirus outbreak until the outbreak of the Delta variant. However, during the Omicron variant outbreak, it was reported that other diseases than pneumonia became the main causes of death, such as exacerbation of the underlying disease that had been present before hospitalization and the onset of other complications during hospitalization.

Concerning the spread of infection last summer, there has been a continuing decrease in the rate of severe cases and increase in the ratio of elderly people among hospitalized patients as during the previous outbreak compared to spreading of the infection in the summer of 2021. Among the deaths during the 2022 summer outbreak, mechanical ventilation/nasal high flow use rates and steroid prescription rates were decreased compared to the 2021 outbreak.

Among the fatal cases of infected children who died of endogenous factors, there were some cases without any underlying diseases. The reports on the results of on-site investigations have stated that it is necessary to pay attention to neurological symptoms such as convulsions and disturbance of consciousness, and systemic symptoms such as vomiting and poor oral intake besides the respiratory symptoms.

Among the deaths that occurred at home in July and August last year, approximately 80% of the patients were 70 years and older, which is similar to the trend of all deaths during the same period. It suggests that there were also many deaths caused by other factors than COVID-19. In addition, according to the status of handling dead bodies known to be coronavirus positive, the number reported monthly has been the highest during the last December. The proportion of deaths due to coronavirus has recently reached approximately 30%. The local governments are developing treatment, testing and follow-up outpatient medical care systems including medical institutions. It is important to continuously endeavor to provide the necessary medical care to home care patients.

According to Japanese data, the risk of infection remains until 10 days after onset, and infectivity is high until 7 days after onset. Even after waiting for 5 days, a third of patients are still shedding infectious viruses. On Day 8 (after isolation for 7 days), most patients (approximately 85%) did not shed infectious viruses, and it was reported that even if patients did shed the virus, the amount of virus decreased to one-sixth that in the initial stage of onset after 7 days.

Concerning the conventional vaccine, the infection and disease onset prevention effects of the first vaccination against the Omicron variant are markedly reduced. The hospitalization-preventing effect is reported maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing, disease onset-preventing and hospitalization-preventing effects against infection with the Omicron variant, and information on how these vaccine effects are attenuated after a third vaccination has become available. Concerning the vaccine against the Omicron variant (BA.4-5), it has been reported that the preventive effect against disease onset was observed within 0 to 2 months (median 1 month) after vaccination.

While the BA.5 lineage continues to be mainstream in the world, there are many reports of sublineages of the Omicron variant and recombinants with characteristic mutations in the spike protein. There are also sublineages for which superiority in the increase in infected patients has been indicated, including the BQ.1 lineage (sublineages of the BA.5.3 lineage), as well as the XBB lineage (sublineages of the BJ.1 lineage [sublineage of the BA.2.10 lineage] and recombinants of the BM.1.1.1 lineage [sublineage of the BA.2.75.3 lineage]). In Europe, an increase in the proportion of the BQ.1 lineage has been confirmed, which is also increasing in Japan. In addition, the XBB.1.5 lineage (sublineages of the XBB lineage) is on an increasing trend in the US. The World Health Organization (WHO), etc., pointed out that the immune escape of these variants probably leads to dominance in the increasing number of infected cases, but the information obtained so far suggest that there is limited epidemiological and clinical knowledge of the infectivity and severity of the XBB.1.5 lineage. There are also no clear findings on the BN.1.2 and BN.1.3 lineages, which have been increasing in Japan. It is necessary to continue to collect data and analyze the situation and findings in other countries regarding these characteristics of the new sublineages and recombinants, and to continue monitoring by genome surveillance.

With the promotion of vaccination, the proportion of immune carriers against the Omicron variant (BA.4-5) shows an increase in each age group, and it has been reported that the percentage is increasing particularly in the elderly population. However, immunity acquired both through vaccination and natural infection may decline over time.

As in usual years, the nighttime population decreases greatly during the year-end and New Year holidays in most areas including large cities.

Currently, the BA.5 lineage is the mainstream in Japan, but sublineages of the Omicron variant such as BQ.1 and XBB lineages are considered to have greater immune escape ability, and have been pointed out to predominate among the increasing number of infected people overseas. Particularly regarding the BQ.1 lineage, the proportion is domestically increasing, and close attention is required.

With a full-fledged winter, temperatures are lowering nationwide, and ventilation may be difficult. Respiratory virus infections also tend to be prevalent in winter.

• As for the “vaccine for the Omicron variant," vaccination of all persons aged 12 and over who have completed the first vaccination should proceed.
• As both vaccines for the BA.1 and the BA.4 and BA.5 lineages are expected to be more effective than the previous vaccines, it is necessary to proceed with vaccination with the vaccine that can be given sooner. All eligible persons who wish to receive vaccination will be asked to receive the vaccine for the Omicron variant.
• Those who have not received vaccination will be encouraged to consider getting the initial vaccination as soon as possible.
• For children (ages 5 to 11), booster vaccinations will be promoted along with the initial vaccination. For children (ages 6 months to 4 years), initial vaccinations will be promoted.
• It is necessary to discuss promptly how to position the coronavirus vaccination in the future.

• The national and local governments are required to secure a system that enables testing and should further utilize testing.
• Perform frequent tests (about 2 or 3 times a week for facility workers) for workers at facilities for elderly people.
• Establishment of a system for fever outpatients should be further promoted, so that patients with symptoms can self-test using an antigen qualitative test kit, and if the result is positive, they can promptly undergo health observation at a health follow-up center, etc.
• Further promotion of the utilization of antigen qualitative test kits, which have been switched to OTC and are sold on the internet.

• The status of the COVID-19 in China is rapidly worsening, making it difficult to grasp the detailed situation. Based on this situation, temporary measures such as immigration inspections have been implemented since December 30, 2022 to avoid a sharp increase in the inflow of the COVID-19 into Japan, and flexible responses will be taken while monitoring the infection situation in China.

In winter, it is also the time when the number of patients with diseases other than the COVID-19 increases. With the support of the national government, prefectural governments must take measures mainly to avoid overcrowding of hospital beds and fever outpatient clinics as follows.

• Maintain the total number of beds required for patients infected with the COVID-19 based on the bed securing plan, and promptly increase the number of beds in response to spreading of the infection. In addition, continue to increase the number of medical institutions that can handle COVID-19 by supporting improvement of the ability to treat COVID-19 cases, even at hospitals without any beds for infected patients (promotion of zoning of hospital rooms, etc.).
• In addition to facilitating the use of available hospital beds and developing temporary medical facilities to supplement hospital beds, making efforts to avoid a shortage of hospital beds and emergency medical care, such as utilization of lodging facilities and resting beds
• Appropriate adjustment so that patients who need hospital treatment can be hospitalized preferentially (securing and expanding logistical support hospitals, and improving the hospital turnover rate, such as by dissemination of the standard for early discharge of 4 days, as a rule), implementation of frequent examinations at facilities for elderly people and others, and further strengthening medical support during normal times
• In addition to extending the office hours and the number of outpatient clinics for fever patients, the outpatient medical care system is strengthened and prioritized by strengthening regional outpatient and testing centers and telephone and online clinics, etc.
• Local residents should be informed that they should refrain from visiting emergency outpatient units only to receive a precautionary examination if they do not have symptoms, for example, taking the actual situation in the region into consideration, so that nobody is prevented from receiving treatment. To respond to concerns and questions when a patient’s physical condition deteriorates, the telephone consultation service by healthcare professionals should be thoroughly publicized, and this service should also be strengthened.
• Ensuring that workplaces and schools do not require test certificates at the start of medical treatment

• Assuming that there are many patients with fever during simultaneous epidemics, the following efforts should be promoted according to the actual situation in each region: strengthening of fever outpatient clinics, strengthening of telephone consultations and telemedicine in preparation for overcrowding of the fever outpatient clinics, expansion of health follow-up centers, securing of self-examination kits, strengthening of the consultation system, and prevention of overcrowded emergency medical care.Furthermore, the smooth supply of therapeutic drugs will be promoted, including oral drugs that are new treatment options for COVID-19 and are prescribed after confirmation of the indication by a doctor. Pharmacies, etc. will be asked to use the consultation service of the Ministry of Health, Labour and Welfare when it is difficult to obtain antipyretic analgesics.
• The prefectures will work to strengthen and prioritize the health care system based on plans to establish systems such as strengthening of outpatient medical care systems in accordance with the actual conditions in each region.
• It is necessary to provide information and appropriate messages depending on the status of infection to the public. In addition to calling for preparations such as purchasing the antigen qualitative test kits and antipyretic analgesics, checking the contact information of consultation services, etc., persons at a low risk of severe symptoms will be encouraged to perform self-testing or to utilize their local health follow-up centers. While the emergency medical care system is usually overwhelmed in winter, people will be advised to do the following: check the “guide for ambulance services” in preparation for an acute illness or injury, consult a family doctor when hesitant to call an ambulance, use a telephone consultation service such as #7119, and call an ambulance without hesitation if necessary.
• At the same time, vaccination against COVID-19 and seasonal influenza of those who are subject to vaccination should be promoted.
• When the number of infected cases sharply increases and hospitals are overcrowded, measures depending on the situation are required, including requests/calls for residents and business operators to prevent spreading of the infection and to maintain the functions of the medical system, as well as highly effective measures to prevent the spread of infection including behavioral restrictions.

• It is necessary to promptly promote consideration of effective and appropriate surveillance to grasp the epidemic status. It is also necessary to continue monitoring of the trends of variants through genomic surveillance.
• Regarding the risk assessment of COVID-19, it is necessary to continue evaluation of the pathogenicity, infectivity, mutations, etc.

• It is necessary to publicize and recommend effective ventilation methods to prevent insufficient indoor ventilation (how to create airflow considering aerosols and install partitions that do not block airflow, for example) due to the use of heating appliances due to low temperatures.

Re-inspection and implementation of the following basic infection control measures are needed.

• Continue proper wearing of nonwoven masks according to the situation, hand hygiene, thorough ventilation, etc.
• Avoid situations with a high risk of infection, such as the three Cs, congestion, or loud voices.
• In the event of a meeting at a restaurant, choose a venue certified by a third party, keep the number of people as low as possible, avoid speaking in loud voices and staying for a long time, and wear a mask when talking.
• People with symptoms such as sore throat, cough, and fever should refrain from going out.
• Refer to guidelines for hospital visits and use of an ambulance.
• Prepare antigen qualitative test kits and antipyretic analgesics at home, and check the contact information of consultation services.
• To reduce the chances of contact as far as possible, it is necessary for measures at the workplace, such as again promoting the use of telework.
• Organizers of events or meetings should fully evaluate the epidemic situation and risk of infection in the area, and consider whether or not to hold the event. If the event is held, measures should be taken to minimize the infection risk.
• Since the risk of infection remains during the shortened period of home care of those who test positive, they should monitor their own physical condition, such as measuring their own temperature, and taking thorough measures against infection when going out. They must also be asked to avoid contact with people who are at risk of severe disease, such as elderly people.
• To allow the minimum necessary outings, such as shopping for groceries, after 24 hours have passed since symptoms have subsided or when there are no symptoms, it is necessary to take voluntary actions to prevent infection, such as wearing a mask when going out, keeping contact with other people at the minimum period of time necessary, and not using public transportation.

It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.

In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to the mucosa, aerosol inhalation, contact infection, etc.).

It has been shown that infection with the Omicron variant may present a relatively lower risk of hospitalization and aggravation than with the Delta variant. To evaluate COVID-19, including the Omicron variant, it is not only necessary to assess the severity as a disease but also of the transmissibility and the impact on the medical care system and society as a whole.

Concerning the death toll since the outbreak at the end of 2021, it is reported that the novel coronavirus is not the direct cause of death in quite a number of cases compared to the epidemic in the summer of 2021; for example, when elderly people who had been living in a facility for elderly people since before the infection were infected and died, the death was due to worsening of the underlying disease. There were many cases of serious respiratory failure due to typical viral pneumonia caused by the novel coronavirus infection from the beginning of the novel coronavirus outbreak until the outbreak of the Delta variant. However, during the Omicron variant outbreak, it was reported that other diseases than pneumonia became the main causes of death, such as exacerbation of the underlying disease that had been present before hospitalization and the onset of other complications during hospitalization.

Concerning the spread of infection last summer, there has been a continuing decrease in the rate of severe cases and increase in the ratio of elderly people among hospitalized patients as during the previous outbreak compared to spreading of the infection in the summer of 2021. Among the deaths during the 2022 summer outbreak, mechanical ventilation/nasal high flow use rates and steroid prescription rates were decreased compared to the 2021 outbreak.

Among the fatal cases of infected children who died of endogenous factors, there were some cases without any underlying diseases. The reports on the results of on-site investigations have stated that it is necessary to pay attention to neurological symptoms such as convulsions and disturbance of consciousness, and systemic symptoms such as vomiting and poor oral intake besides the respiratory symptoms.

Among the deaths that occurred at home in July and August last year, approximately 80% of the patients were 70 years and older, which is similar to the trend of all deaths during the same period. It suggests that there were also many deaths caused by other factors than COVID-19. The local governments are developing treatment, testing and follow-up outpatient medical care systems including medical institutions. It is important to continuously endeavor to provide the necessary medical care to home care patients.

According to Japanese data, the risk of infection remains until 10 days after onset, and infectivity is high until 7 days after onset. Even after waiting for 5 days, a third of patients are still shedding infectious viruses. On Day 8 (after isolation for 7 days), most patients (approximately 85%) did not shed infectious viruses, and it was reported that even if patients did shed the virus, the amount of virus decreased to one-sixth that in the initial stage of onset after 7 days.

Concerning the conventional vaccine, the infection and disease onset prevention effects of the first vaccination against the Omicron variant are markedly reduced. The hospitalization-preventing effect is reported maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing, disease onset-preventing and hospitalization-preventing effects against infection with the Omicron variant, and information on how these vaccine effects are attenuated after a third vaccination has become available. Concerning the vaccine against the Omicron variant (BA.4-5), it has been reported that the preventive effect against disease onset was observed within 0 to 2 months (median 1 month) after vaccination.

While the BA.5 lineage continues to be mainstream in the world, there are many reports of sublineages of the Omicron variant and recombinants with characteristic mutations in the spike protein. There are also sublineages for which superiority in an increase in infected patients has been indicated, including the BQ.1 lineage (sublineages of the BA.5.3 lineage), as well as the XBB lineage (sublineages of the BJ.1 lineage [sublineage of the BA.2.10 lineage] and recombinants of the BM.1.1.1 lineage [sublineage of the BA.2.75.3 lineage]). In Europe, an increase in the proportion of the BQ.1 lineage has been confirmed, which is also increasing in Japan. In addition, the XBB.1.5 lineage (sublineages of the XBB lineage) is on an increasing trend in the US. The World Health Organization (WHO), etc., pointed out that the immune escape of these variants probably leads to dominance in the increasing number of infected cases, but the information obtained so far suggest that there is no epidemiological or clinical knowledge of infectivity or severity of the XBB.1.5 lineage. It is necessary to continue to collect data and analyze the situation and findings in other countries regarding these characteristics of the new sublineages and recombinants, and to continue monitoring by genome surveillance.

Immunity acquired both from vaccination and natural infection may decline over time. Although the vaccination rate is higher among people in their 60s and older than in those in their 20s to 40s, the acquisition of immunity by infection is lower, and there is concern about the spread of infection among elderly people.

There are regional differences in the nighttime population, but the number has increased mainly in large cities such as the Tokyo metropolitan area, Aichi, Osaka, and Fukuoka, compared to the same period last year. There are also concerns about increased opportunities for contact during the year-end and New Year holidays.

Currently, the BA.5 lineage is the mainstream in Japan, but sublineages of the Omicron variant such as the BQ.1 and XBB lineages are considered to have greater immune escape ability, and it has been pointed out that these are predominant in the increasing number of infected people overseas. Regarding the BQ.1 lineage, in particular, the domestic ratio is increasing, and close attention is required.

As winter is approaching and temperatures are dropping nationwide, ventilation may be difficult. In addition, respiratory virus infections tend to be prevalent in winter.

• As for the “vaccine for the Omicron variant," vaccination of all persons aged 12 and over who have completed the first vaccination should proceed.
• Vaccination against the BA.4 and BA.5 lineages has also started. As both vaccines for the BA.1 and the BA.4 and BA.5 lineages are expected to be more effective than the previous vaccines, it is necessary to proceed with vaccination with the vaccine that can be given sooner. As the vaccination interval from the last vaccination was shortened from at least 5 to at least 3 months, all eligible persons who wish to receive vaccination will be asked to receive the vaccine for the Omicron variant within this year.
• Those who have not received vaccination will be encouraged to consider getting the initial vaccination as soon as possible.
• For children (ages 5 to 11), booster vaccinations will be promoted along with the initial vaccination. For children (ages 6 months to 4 years), initial vaccinations will be promoted.
• It is necessary to discuss promptly how to position the coronavirus vaccination in the future.

• The national and local governments are required to secure a system that enables testing, and should further utilize testing.
• Perform frequent tests (about 2 or 3 times a week for facility workers) for workers at facilities for elderly people.
• Establishment of a system for fever outpatients should be further promoted, so that patients with symptoms can self-test using an antigen qualitative test kit, and if the result is positive, they can promptly undergo health observation at a health follow-up center, etc.
• Further promotion of the utilization of antigen qualitative test kits, which have been switched to OTC and are sold on the internet.

Prefectural governments must take measures to avoid overcrowding of beds and fever outpatient sections with the support of the national government.

• Maintain the total number of beds required for patients infected with the COVID-19 based on the bed securing plan. When the infection spreads, increase the number of beds without delay. Also, continue to increase the number of medical institutions that can handle the COVID-19, even hospitals that have no beds for COVID-19, by supporting the improvement of the ability to respond to COVID-19 patients (promotion of zoning hospital room, etc.).
• In addition to facilitating the use of available hospital beds and developing temporary medical facilities to supplement hospital beds, making efforts to avoid a shortage of hospital beds and emergency medical care, such as utilization of lodging facilities and resting beds
• Appropriate adjustment so that patients who need hospital treatment can be hospitalized preferentially (securing and expanding logistical support hospitals, and improving the hospital turnover rate, such as by dissemination of the standard for early discharge of 4 days, as a rule), implementation of frequent examinations at facilities for elderly people and others, and further strengthening medical support during normal times
• In addition to extending the office hours and the number of outpatient clinics for fever patients, the outpatient medical care system is strengthened and prioritized by strengthening regional outpatient and testing centers and telephone and online clinics, etc.
• Local residents should be informed that they should refrain from visiting an emergency outpatient unit only to receive a precautionary examination without symptoms, according to the actual situation in the region. In addition, in order to respond to concerns and questions at the time of worsening physical conditions, the consultation service by healthcare professionals via telephone should be thoroughly publicized, and this service should also be strengthened.
• Ensuring that workplaces and schools do not require test certificates at the start of medical treatment

• Assuming that there are also many patients with fever during simultaneous epidemics, the following measures should be promoted according to the actual situation of each region: strengthening of fever outpatient clinics, strengthening of telephone and online examination services in preparation for cases of overcrowding at fever outpatient clinics, expansion of health follow-up centers, securing of self-examination kits, and strengthening of the consultation system. The smooth supply of therapeutic drugs will be promoted, including oral drugs that are new treatment options for COVID-19 which are prescribed after confirmation the indication by a doctor.
• The prefectures will work to strengthen and prioritize the health care system based on plans to establish systems such as strengthening of outpatient medical care systems in accordance with the actual conditions in each region.
• It is necessary to provide information to the public, as well as appropriate messages according to the status of infection. In addition to calling for early preparation of conventional antigen qualitative test kits and antipyretic analgesics, patients are encouraged to visit outpatient clinics or receive treatment according to the risk of severity.
• To prevent the infections from becoming severe as far as possible, vaccination against COVID-19 and seasonal influenza should be promoted among the target population for vaccination.
• In case the number of infected persons sharply increases and hospitals are overcrowded, or changes in the characteristics of the viruses increase their pathogenicity, measures depending on the situation are required, including requests/calls for residents and business operators to prevent spreading of the infection and to maintain the functions of the medical system, as well as highly effective measures to prevent the spread of infection including behavioral restrictions.

• Deterioration of the accuracy of current surveillance is a concern due to the limited scope of notification, prioritization of notification items, delays in testing and diagnosis/reporting due to many infections, and changes in healthcare-seeking behavior. It is necessary to promptly promote consideration of effective and appropriate surveillance to grasp the epidemic status. It is also necessary to continue monitoring the trends of variants through genomic surveillance.
• Regarding risk assessment, it is necessary to promptly investigate the pathogenicity, infectivity, mutation, etc. of COVID-19.

• It is necessary to publicize and recommend effective ventilation methods to prevent insufficient indoor ventilation (how to create airflow considering aerosols, installation of partitions that do not block airflow, etc.).

Re-inspection and implementation of the following basic infection control measures are needed.

• Continue proper wearing of nonwoven masks according to the situation, hand hygiene, thorough ventilation, etc.
• Avoid situations with a high risk of infection, such as the three Cs, congestion, or loud voices.
• For year-end and New Year parties at restaurants, choose a venue certified by a third party, keep the number of people as small as possible, avoid loud voices and staying a long time, and wear masks when talking.
• People with symptoms such as sore throat, cough, and fever should refrain from going out.
• Refer to guidelines for hospital visits and use of an ambulance.
• Prepare antigen qualitative test kits/antipyretic analgesic at home, etc.
• To reduce the chances of contact as far as possible, it is necessary for measures at the workplace, such as again promoting the use of telework.
• Organizers of events or meetings should fully evaluate the epidemic situation and risk of infection in the area, and consider whether or not to hold the event. If the event is held, measures should be taken to minimize the infection risk.
• Since the risk of infection remains during the shortened period of home care of those who test positive, they should monitor their own physical condition, such as measuring their own temperature, and taking thorough measures against infection when going out. They must also be asked to avoid contact with people who are at risk of severe disease, such as elderly people.
• To allow the minimum necessary outings, such as shopping for groceries, after 24 hours have passed since symptoms have subsided or when there are no symptoms, it is necessary to take voluntary actions to prevent infection, such as wearing a mask when going out, keeping contact with other people at the minimum period of time necessary, and not using public transportation.

It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.

In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors, eating and drinking, in locations with inadequate ventilation, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to the mucosa, aerosol inhalation, contact infection, etc.).

It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than with the Delta variant. However, analyses to date show that there are more deaths due to infection with the Omicron variant than due to seasonal influenza. It also seems as if the incidence of pneumonia is higher than in case of seasonal influenza, but given the limited data, it has to be investigated by various analyses.

Concerning the death toll from the outbreak since the end of last year, it is reported that there are many cases in which the novel coronavirus is not the direct cause of death compared to last summer's outbreak, for example, elderly people who have been in a facility for the elderly before the infection are infected but die due to worsening of the underlying disease. There were many cases of serious respiratory failure due to typical viral pneumonia caused by novel coronavirus infection from the beginning of the novel coronavirus outbreak until the Delta variant outbreak. However, during the Omicron variant outbreak, it was reported that other diseases than pneumonia formed the main causes of death, such as exacerbation of the underlying disease that was present before hospitalization and the onset of other complications during hospitalization.

During spread of the infection this summer, the rate of severe cases decreased compared to that during the previous outbreak and the ratio of elderly people among hospitalized patients increased compared to last summer's outbreak. Among the deaths during this summer’s outbreak, mechanical ventilation/nasal high flow use rates and steroid prescription rates have decreased compared to the outbreak from the end of last year.

Fatal cases among infected children in whom the cause of death was identified included cases without underlying disease. Preliminary reports on the results of on-site investigations have stated that it is necessary to pay attention to neurological symptoms such as convulsions and disturbance of consciousness, and other systemic symptoms than respiratory symptoms, such as vomiting and poor oral intake.

Among deaths that occurred at home in July and August, approximately 80% of the patients were 70 years and older, which is similar to the trend of all deaths during the same period, suggesting that many patients die from other factors than the novel coronavirus. Local governments are developing outpatient medical care systems including medical examinations/testing institutions and health follow-up systems, and it is important to continuously make efforts to provide the necessary medical care to patients at home.

According to the Japanese data, the risk of infection remains until 10 days after onset, and infectivity is high until 7 days after onset. Even after waiting for 5 days, a third of the patients are still shedding infectious viruses. On Day 8 (after isolation for 7 days), most patients (approximately 85%) did not shed infectious viruses, and it was reported that even if patients did shed the virus, the amount of virus decreased to one-sixth that in the initial stage of onset after 7 days.

Concerning the conventional vaccine, the infection and disease onset prevention effects of the first vaccination against the Omicron variant are markedly reduced. The hospitalization-preventing effect is reported maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing, disease onset-preventing and hospitalization-preventing effects against infection with the Omicron variant, and information on how these vaccine effects are attenuated after a third vaccination has become available. Concerning the vaccine against the Omicron variant (BA. 4-5), it has been reported that the preventive effect against disease onset was observed within 0 to 2 months (median 1 month) after vaccination.

While the BA.5 lineage continues to be mainstream in the world, there are many reports of sublineages of the Omicron variant and recombinants with characteristic mutations in the spike protein. There are also sublineages for which superiority in an increase in infected patients has been indicated, including the BQ.1 lineage (sublineages of the BA.5.3 lineage), which are frequently reported in Europe and the United States, as well as the XBB lineage (recombinant of the BJ.1 lineage [sublineage of the BA.2.10 lineage] and the BM.1.1.1 lineage [sublineage of the BA.2.75.3 lineage]), which has been reported mainly in India and Singapore. In Europe and the United States, the proportion of the BQ.1 lineage is increasing in some countries, including Japan. The World Health Organization (WHO), etc., points out that the immune escape of these variants may lead to dominance in increasing the number of infected persons, but the information obtained so far does not suggest that either the infectivity or seriousness of the variants is increasing. It is necessary to continue to collect data and analyze the situation and findings in other countries regarding these characteristics of the new sublineages and recombinants, and to continue monitoring by genome surveillance.

Immunity acquired both from vaccination and natural infection may decline over time. Although the vaccination rate is higher among people in their 60s and older than those in their 20s to 40s, the acquisition of immunity by infection is lower, and there is concern about the spread of infection among elderly people. Although the antibody prevalence in the Japanese public, which is based on a survey of antibody prevalence using donated blood samples, is important data, it is simply a preliminary report, and it must be evaluated based on more detailed analysis in the future.

There are regional differences in the nighttime population, but it is currently trending upward in many regions, including western Japan, and has remained the same or higher compared to the same period last year. Some regions have reached the level before the spread of COVID-19, and there is concern about increased contact opportunities due to the reactivation of socioeconomic activities toward the end of the year.

Currently, the BA.5 lineage is the mainstream in Japan, but the sublineages of the Omicron variant such as BQ.1 and XBB lineages are considered to have greater immune escape ability, and have been pointed out to be predominant in increasing the number of infected people overseas. Particularly regarding the BQ.1 lineage, the proportion may further increase in Japan in the future, and close attention is required.

Temperatures are dropping nationwide including northern Japan, and ventilation may be difficult. In addition, respiratory virus infections tend to be prevalent in winter.

• As for the “vaccine for the Omicron variant," vaccination of all persons aged 12 and over who have completed the first vaccination should proceed.
• Vaccination for the BA.4 and BA.5 lineages has also started. As both vaccines for the BA.1 and the BA.4 and BA.5 lineages are expected to be more effective than the previous vaccines, it is necessary to proceed with vaccination with the vaccine that can be given sooner. As the vaccination interval from the last vaccination was shortened from at least 5 to at least 3 months, all eligible persons who wish to receive vaccination will be asked to receive the vaccine for the Omicron variant within this year.
• Those who have not received vaccination will be encouraged to consider getting the initial vaccination as soon as possible.
• For children (ages 5 to 11), booster vaccinations will be promoted along with the initial vaccination.
• The initial vaccination for children (aged 6 months to 4 years) has been approved by the PMDA and positioned as an extraordinary vaccination, and initial vaccination in this age group will proceed.

• The national and local governments are required to secure a system that enables testing, and should further utilize testing.
• Perform frequent tests (about 2 or 3 times a week for facility workers) for workers at facilities for elderly people.
• Establishment of a system for fever outpatients should be further promoted, so that patients with symptoms can self-test using an antigen qualitative test kit, and if the result is positive, they can promptly undergo health observation at a health follow-up center, etc.
• Further promotion of the utilization of antigen qualitative test kits, which have been switched to OTC and are sold on the internet.

Prefectural governments must take measures to avoid overcrowding of beds and fever outpatient sections with the support of the national government.

• Maintain the total number of beds required for patients infected with the COVID-19 based on the bed securing plan. When the infection spreads, increase the number of beds without delay. Also, continue to increase the number of medical institutions that can handle the COVID-19, even hospitals that have no beds for COVID-19, by supporting the improvement of the ability to respond to COVID-19 patients (promotion of zoning hospital room, etc.).
• In addition to facilitating the use of available hospital beds and developing temporary medical facilities to supplement hospital beds, making efforts to avoid a shortage of hospital beds and emergency medical care, such as utilization of lodging facilities and resting beds
• Appropriate adjustment so that patients who need hospital treatment can be hospitalized preferentially (securing and expanding logistical support hospitals, and improving the hospital turnover rate, such as by dissemination of the standard for early discharge of 4 days, as a rule), implementation of frequent examinations at facilities for elderly people and others, and further strengthening medical support during normal times
• Expansion and promotion of fever outpatient services, including the use of online medical care, etc.
• Local residents should be informed that they should refrain from visiting an emergency outpatient unit only to receive a precautionary examination without symptoms, according to the actual situation in the region. In addition, in order to respond to concerns and questions at the time of worsening physical conditions, the consultation service by healthcare professionals via telephone should be thoroughly publicized, and this service should also be strengthened.
• Ensuring that workplaces and schools do not require test certificates at the start of medical treatment

• Assuming that there are also many patients with fever during simultaneous epidemics, the following measures should be promoted according to the actual situation of each region: strengthening of fever outpatient clinics, strengthening of telephone and online examination services in preparation for cases of overcrowding at fever outpatient clinics, expansion of health follow-up centers, securing of self-examination kits, and strengthening of the consultation system.The smooth supply of therapeutic drugs will be promoted, including oral drugs that are new treatment options for COVID-19 which are prescribed after confirmation the indication by a doctor.
• The prefectures will formulate plans to establish systems such as strengthening of outpatient medical care systems in accordance with the actual conditions in each region, and will work to strengthen and prioritize the health care system.
• It is necessary to provide information to the public, as well as appropriate messages according to the status of infection. In addition to calling for early preparation of conventional antigen qualitative test kits and antipyretic analgesics, patients are encouraged to visit outpatient clinics or receive treatment according to the risk of severity.
• To prevent the infections from becoming severe as far as possible, vaccination against COVID-19 and seasonal influenza should be promoted among the target population for vaccination.
• In case the number of infected persons sharply increases and hospitals are overcrowded, or changes in the characteristics of the viruses increase their pathogenicity, measures depending on the situation are required, including requests/calls for residents and business operators to prevent spreading of the infection and to maintain the functions of the medical system, as well as highly effective measures to prevent the spread of infection including behavioral restrictions.

• Deterioration of the accuracy of current surveillance is a concern due to the limited scope of notification, prioritization of notification items, delays in testing and diagnosis/reporting due to many infections, and changes in healthcare-seeking behavior. It is necessary to promptly promote consideration of effective and appropriate surveillance to grasp the epidemic status. It is also necessary to continue monitoring the trends of variants through genomic surveillance.
• Regarding risk assessment, it is necessary to promptly investigate the pathogenicity, infectivity, mutation, etc. of COVID-19.

• It is necessary to publicize and recommend effective ventilation methods to prevent insufficient indoor ventilation (how to create airflow considering aerosols, installation of partitions that do not block airflow, etc.).

Re-inspection and implementation of the following basic infection control measures are needed.

• Continue proper wearing of nonwoven masks according to the situation, hand hygiene, thorough ventilation, etc.
• Avoid situations with a high risk of infection, such as the three Cs, congestion, or loud voices.
• For year-end and New Year parties at restaurants, choose a venue certified by a third party, keep the number of people as small as possible, avoid loud voices and staying a long time, and wear masks when talking.
• People with symptoms such as sore throat, cough, and fever should refrain from going out.
• Refer to guidelines for hospital visits and use of an ambulance.
• Prepare antigen qualitative test kits/antipyretic analgesic at home, etc.
• To reduce the chances of contact as far as possible, it is necessary for measures at the workplace, such as again promoting the use of telework.
• Organizers of events or meetings should fully evaluate the epidemic situation and risk of infection in the area, and consider whether or not to hold the event. If the event is held, measures should be taken to minimize the infection risk.
• Since the risk of infection remains during the shortened period of home care of those who test positive, they should monitor their own physical condition, such as measuring their own temperature, and taking thorough measures against infection when going out. They must also be asked to avoid contact with people who are at risk of severe disease, such as elderly people.
• To allow the minimum necessary outings, such as shopping for groceries, after 24 hours have passed since symptoms have subsided or when there are no symptoms, it is necessary to take voluntary actions to prevent infection, such as wearing a mask when going out, keeping contact with other people at the minimum period of time necessary, and not using public transportation.

It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.

In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to the mucosa, aerosol inhalation, contact infection, etc.).

It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than with the Delta variant. However, analyses to date show that there are more deaths due to infection with the Omicron variant than seasonal influenza. It also seems as if the incidence of pneumonia is higher than that of seasonal influenza, but given the limited data, it needs to be investigated by various analyses.

Concerning the death toll from the outbreak since the end of last year, it is reported that there are many cases in which the novel coronavirus is not the direct cause of death compared to last summer's outbreak, for example, elderly people who have been in a facility for the elderly before the infection are infected but die due to worsening of the underlying disease. There were many cases of serious respiratory failure due to typical viral pneumonia caused by novel coronavirus infection from the beginning of the novel coronavirus outbreak until the Delta variant outbreak. However, during the Omicron variant outbreak, it was reported that other diseases than pneumonia are the main causes of death, such as exacerbation of the underlying disease that was present before hospitalization and the onset of other complications during hospitalization. In the spread of infection this summer, the rate of severe cases has decreased compared to the previous outbreak and the ratio of elderly people among hospitalized patients has increased compared to last summer's outbreak. Among the deaths during this summer’s outbreak, mechanical ventilation/nasal high flow use rates and steroid prescription rates have decreased compared to the outbreak from the end of last year.

Fatal cases among infected children in whom endogenous death was identified included cases without underlying diseases. Preliminary reports on the results of on-site investigations have stated that it is necessary to pay attention to neurological symptoms such as convulsions and disturbance of consciousness, and other systemic symptoms than respiratory symptoms, such as vomiting and poor oral intake.

According to Japanese data, risk of infection remains until 10 days after onset, and infectivity is high until 7 days after onset. Even after waiting for 5 days, 1/3 of patients are still shedding infectious viruses. On Day 8 (after waiting 7 days), most patients (approximately 85%) had not shed infectious virus, and it was reported that even in those who shed the virus, the amount of virus decreased to one-sixth after 7 days compared to the initial stage.

For infection with the Omicron variant, the preventive effects of a first vaccination against infection and disease onset are markedly reduced. Its preventive effect on hospitalization is reported to be maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing effect, onset-preventing effect, and hospitalization-preventing effect against infection by the Omicron variant, and information on how these vaccine effects are attenuated after a third vaccination has become available. Regarding the fourth vaccination, it has been reported that while the aggravation-preventing effect was not reduced for 6 weeks, the infection-preventing effect lasted only for a short time.

While the BA.5 lineage continues to be mainstream in the world, there are many reports of sublineages of the Omicron variant and recombinants which have characteristic mutations in the spike protein. There are also sublineages for which superiority in an increase in infected patients has been indicated, including the BQ.1 and BQ.1.1 lineages (sublineages of the BA.5.3 lineage), which are frequently reported in Europe and the United States, as well as the XBB lineage (recombinant of the BJ.1 lineage [sublineages of the BA.2.10 lineage] and the BM.1.1.1 lineage [sublineages of the BA.2.75.3 lineage]), which has been reported mainly in India and Singapore. In Europe and the United States, the proportion of BQ.1 and BQ.1.1 lineages is increasing in some countries, and it is expected that the proportion will increase further in the future, but at present, a significant increase in the number of infected persons has not been confirmed. The World Health Organization (WHO), etc., points out that the immune escape of these variants may lead to dominance in increasing the number of infected persons, but the information obtained so far does not suggest that either the infectivity or seriousness of the variants is increasing. It is necessary to continue to collect data and analyze the situation and findings in other countries regarding these characteristics of the new sublineages and recombinants, and to continue monitoring by genome surveillance.

Immunity acquired both from vaccination and natural infection may decline over time. Although the vaccination rate is higher among people in their 60s and older than those in their 20s to 40s, the acquisition of immunity by infection is lower, and there is concern about the spread of infection among elderly people.

There are regional differences in the nighttime population, but the number has remained the same or higher in many regions compared to the same period last year. Some regions have seen rapid increase and reached the level before the spread of COVID-19, and there is concern about increased contact opportunities due to the reactivation of socioeconomic activities toward the end of the year.

In Japan, the BA.5 lineage has largely become mainstream. It is necessary to pay close attention to the strains that have been pointed out to be dominant in the increase in the number of infected persons overseas, such as the BQ.1 and XBB lineages, as the proportion may increase further in the future.

Nationwide, weather conditions are favorable for ventilation, but proper ventilation may be difficult in some regions like northern Japan due to a decline in temperature in the days ahead. In addition, respiratory virus infections tend to increase in winter.

• As for the “vaccine for the Omicron variant," vaccination of all persons aged 12 and older who have completed the first vaccination should proceed.
• Vaccination for the BA.4 and BA.5 lineages has also started. As both vaccines for the BA.1 and the BA.4 and BA.5 lineages are expected to be more effective than the previous vaccines, it is necessary to proceed with vaccination with the vaccine that can be given sooner. As the vaccination interval from the last vaccination was shortened from at least 5 to at least 3 months, all eligible persons who wish to receive vaccination will be asked to receive the vaccine for the Omicron variant within this year.
• Those who have not received vaccination will be encouraged to consider getting the initial vaccination as soon as possible.
• For children (ages 5 to 11), booster vaccinations will be promoted along with the initial vaccination.
• The initial vaccination for children (aged 6 months to 4 years) has been approved by the PMDA and is positioned as an extraordinary vaccination, and initial vaccination in this age group will proceed.

• The national and local governments are required to secure a system that enables testing and should further utilize testing.
• Performance of frequent tests (about 2 or 3 times a week for facility workers) for workers at facilities for elderly people.
• Establishment of a system for fever outpatients should be further promoted, so that patients with symptoms can self-test using an antigen qualitative test kit, and if the result is positive, they can promptly undergo health observation at a health follow-up center, etc.
• Further promotion of the utilization of antigen qualitative test kits, which have been switched to OTC and are sold on the internet.

Prefectural governments must take measures to avoid overcrowding of beds and fever outpatient clinics with the support of the national government.

• In addition to facilitating the use of available hospital beds and developing temporary medical facilities to supplement hospital beds, making efforts to avoid a shortage of hospital beds and emergency medical care, such as utilization of lodging facilities and resting beds
• Making appropriate adjustments so that patients requiring inpatient treatment can be hospitalized preferentially, performing frequent tests at facilities for elderly people, etc., and further strengthening medical support
• Securing and expanding logistical support hospitals, and improving the hospital turnover rate, such as by dissemination of the standard for early discharge of 4 days, as a rule
• Promotion of effective and less burdensome measures against infection, such as flexible and efficient use of hospital beds through zoning of each hospital room
• Expansion and promotion of fever outpatient services, including the use of online medical care, etc., and further promotion of the development of a “fever outpatient self-examination system”
• Without discouraging the seeking of treatment, local residents should be informed that they should refrain from visiting an emergency outpatient unit only to receive a precautionary examination without symptoms, according to the actual situation in the region. In addition, in order to respond to concerns and questions when physical condition deteriorates, the consultation service by healthcare professionals via telephone should be thoroughly publicized, and this service should also be strengthened.
• Ensuring that workplaces and schools do not require test certificates at the start of medical treatment

• Assuming that there are also many patients with fever during simultaneous epidemics, the following measures should be promoted according to the actual situation of each region: strengthening of fever outpatient clinics, strengthening of telephone and online examination services in preparation for cases of overcrowding at fever outpatient clinics, smooth supply of therapeutic drugs, expansion of health follow-up centers, securing of self-examination kits, and strengthening of the consultation system.
• The prefectures will formulate plans to establish systems such as strengthening of outpatient medical care systems in accordance with the actual conditions in each region, and will work to strengthen and prioritize the health care system before the end of November.
• It is necessary to provide information to the public, as well as appropriate messages according to the status of infection. In addition to calling for early preparation of conventional antigen qualitative test kits and antipyretic analgesics, patients are encouraged to visit outpatient clinics or receive treatment according to the risk of severity.
• To prevent the infections from becoming severe as far as possible, vaccination against the novel coronavirus as well as the influenza virus should also be promoted among the target population for vaccination.
• In case the number of infected persons sharply increases and hospitals are overcrowded, or changes in the characteristics of the viruses increase their pathogenicity, measures depending on the situation are required, including requests/calls for residents and business operators to prevent spreading of the infection and to maintain the functions of the medical system, as well as highly effective measures to prevent the spread of infection including behavioral restrictions.

• Deterioration of the accuracy of current surveillance is a concern due to the limited scope of notification, prioritization of notification items, delays in testing and diagnosis/reporting due to many infections, and changes in healthcare-seeking behavior. It is necessary to promptly promote consideration of effective and appropriate surveillance to grasp the epidemic status.
  It is also necessary to continue monitoring the trends of variants through genomic surveillance.

• It is necessary to publicize and recommend effective ventilation methods to prevent insufficient indoor ventilation (how to create airflow considering aerosols, installation of partitions that do not block airflow, etc.).

Re-inspection and implementation of the following basic infection control measures are needed.

• Continue proper wearing of nonwoven masks according to the situation, hand hygiene, thorough ventilation, etc.
• Avoid situations with a high risk of infection, such as the three Cs, congestion, or loud voices.
• For year-end and New Year parties at restaurants, choose a venue certified by a third party, keep the number of people as small as possible, avoid loud voices and staying a long time, and wear masks when talking.
• People with symptoms such as sore throat, cough, and fever should refrain from going out.
• Refer to guidelines for hospital visits and use of an ambulance.
• Prepare antigen qualitative test kits/antipyretic analgesic at home, etc.
• To reduce the chances of contact as far as possible, it is necessary for measures at the workplace, such as again promoting the use of telework.
• Organizers of events or meetings should fully evaluate the epidemic situation and risk of infection in the area, and consider whether or not to hold the event. If the event is held, measures should be taken to minimize the infection risk.
• Since the risk of infection remains during the shortened period of home care of those who test positive, they should monitor their own physical condition, such as measuring their own temperature, and taking thorough measures against infection when going out. They must also be asked to avoid contact with people who are at risk of severe disease, such as elderly people.
• To allow the minimum necessary outings, such as shopping for groceries, after 24 hours have passed since symptoms have subsided or when there are no symptoms, it is necessary to take voluntary actions to prevent infection, such as wearing a mask when going out, keeping contact with other people at the minimum period of time necessary, and not using public transportation.

It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.

In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to the mucosa, aerosol inhalation, contact infection, etc.).

It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than with the Delta variant. However, analyses to date show that there are more deaths due to infection with the Omicron variant than seasonal influenza. It also seems as if the incidence of pneumonia is higher than that of seasonal influenza, but given the limited data, it needs to be investigated by various analyses.

Concerning the death toll from the outbreak since the end of last year, it is reported that there are many cases in which the novel coronavirus is not the direct cause of death compared to last summer's outbreak, for example, elderly people who have been in a facility for the elderly before the infection are infected but die due to worsening of the underlying disease. There were many cases of serious respiratory failure due to typical viral pneumonia caused by novel coronavirus infection from the beginning of the novel coronavirus outbreak until the Delta variant outbreak. However, during the Omicron variant outbreak, it was reported that other diseases than pneumonia are the main causes of death, such as exacerbation of the underlying disease that was present before hospitalization and the onset of other complications during hospitalization. In the spread of infection this summer, the rate of severe cases has decreased compared to the previous outbreak and the ratio of elderly people among hospitalized patients has increased compared to last summer's outbreak. Among the deaths during this summer’s outbreak, mechanical ventilation/nasal high flow use rates and steroid prescription rates have decreased compared to the outbreak from the end of last year.

Fatal cases among infected children in whom endogenous death was identified included cases without underlying diseases. Preliminary reports on the results of on-site investigations have stated that it is necessary to pay attention to neurological symptoms such as convulsions and disturbance of consciousness, and other systemic symptoms than respiratory symptoms, such as vomiting and poor oral intake.

According to Japanese data, risk of infection remains until 10 days after onset, and infectivity is high until 7 days after onset. Even after waiting for 5 days, 1/3 of patients are still shedding infectious viruses. On Day 8 (after waiting 7 days), most patients (approximately 85%) had not shed infectious virus, and it was reported that even in those who shed the virus, the amount of virus decreased to one-sixth after 7 days compared to the initial stage.

For infection with the Omicron variant, the preventive effects of a first vaccination against infection and disease onset are markedly reduced. Its preventive effect on hospitalization is reported to be maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing effect, onset-preventing effect, and hospitalization-preventing effect against infection by the Omicron variant, and information on how these vaccine effects are attenuated after a third vaccination has become available. Regarding the fourth vaccination, it has been reported that while the aggravation-preventing effect was not reduced for 6 weeks, the infection-preventing effect lasted only for a short time.

While the BA.5 lineage continues to be mainstream in the world, there are many reports of sublineages of the Omicron variant and recombinants which have characteristic mutations in the spike protein. There are also sublineages for which superiority in an increase in infected patients has been indicated, including the BQ.1 and BQ.1.1 lineages (sublineages of the BA.5.3 lineage), which are frequently reported in Europe and the United States, as well as the XBB lineage (recombinant of the BJ.1 lineage [sublineage of the BA.2.10 lineage] and the BM.1.1.1 lineage [sublineage of the BA.2.75.3 lineage]), which has been reported mainly in India and Singapore. In Europe and the United States, the proportion of BQ.1 and BQ.1.1 lineages is increasing in some countries, and it is expected that the proportion will increase further in the future, but at present, a significant increase in the number of infected persons has not been confirmed. The World Health Organization (WHO), etc., points out that the immune escape of these variants may lead to dominance in increasing the number of infected persons, but the information obtained so far does not suggest that either the infectivity or seriousness of the variants is increasing. It is necessary to continue to collect data and analyze the situation and findings in other countries regarding these characteristics of the new sublineages and recombinants, and to continue monitoring by genome surveillance.

Immunity acquired both from vaccination and natural infection may decline over time. Although the vaccination rate is higher among people in their 60s and older than those in their 20s to 40s, the acquisition of immunity by infection is lower, and there is concern about the spread of infection among elderly people.

There are regional differences in the nighttime population, but the number has remained the same or higher in many regions compared to the same period last year. Some regions are rapidly increasing, and there is concern about increased contact opportunities due to the reactivation of socioeconomic activities toward the end of the year.

In Japan, the BA.5 lineage has largely become mainstream. It is necessary to pay close attention to the strains that have been pointed out to be dominant in the increase in the number of infected persons overseas, such as the BQ.1 and XBB lineages, as the proportion may increase further in the future.

Nationwide, weather conditions are favorable for ventilation, but proper ventilation may be difficult in some regions like northern Japan due to a decline in temperature in the days ahead. Respiratory virus infections tend to increase in winter.

• As for the “vaccine for the Omicron variant," vaccination of all persons aged 12 and older who have completed the first vaccination should proceed.
• Vaccination for the BA.4 and BA.5 lineages has also started. As both vaccines for the BA.1 and the BA.4 and BA.5 lineages are expected to be more effective than the previous vaccines, it is necessary to proceed with vaccination with the vaccine that can be given sooner. As the vaccination interval from the last vaccination was shortened from at least 5 to at least 3 months, all eligible persons who wish to receive vaccination will be asked to receive the vaccine for the Omicron variant within this year.
• Those who have not received vaccination will be encouraged to consider getting the initial vaccination as soon as possible.
• For children (ages 5 to 11), booster vaccinations will be promoted along with the initial vaccination.
• The initial vaccination for children (aged 6 months to 4 years) has been approved by the PMDA and is positioned as an extraordinary vaccination, and initial vaccination in this age group will proceed.

• The national and local governments are required to secure a system that enables testing, and should further utilize testing.
• Performance of frequent tests (about 2 or 3 times a week for facility workers) for workers at facilities for elderly people.
• Establishment of a system for fever outpatients should be further promoted, so that patients with symptoms can self-test using an antigen qualitative test kit, and if the result is positive, they can promptly undergo health observation at a health follow-up center, etc.
• Further promotion of the utilization of antigen qualitative test kits, which have been switched to OTC and are sold on the internet.

Prefectural governments must take measures to avoid overcrowding of beds and fever outpatient clinics with the support of the national government.

• In addition to facilitating the use of available hospital beds and developing temporary medical facilities to supplement hospital beds, making efforts to avoid a shortage of hospital beds and emergency medical care, such as utilization of lodging facilities and resting beds
• Making appropriate adjustments so that patients requiring inpatient treatment can be hospitalized preferentially, performing frequent tests at facilities for elderly people, etc., and further strengthening medical support
• Securing and expanding logistical support hospitals, and improving the hospital turnover rate, such as by dissemination of the standard for early discharge of 4 days, as a rule
• Promotion of effective and less burdensome measures against infection, such as flexible and efficient use of hospital beds through zoning of each hospital room
• Expansion and promotion of fever outpatient services, including the use of online medical care, etc., and further promotion of the development of a “fever outpatient self-examination system”
• Without discouraging the seeking of treatment, local residents should be informed that they should refrain from visiting an emergency outpatient unit without symptoms just to receive a precautionary examination, according to the actual situation in the region. In addition, in order to respond to concerns and questions when physical condition deteriorates, the consultation service by healthcare professionals via telephone should be thoroughly publicized, and this service should also be strengthened.
• Ensuring that workplaces and schools do not require test certificates at the start of medical treatment

• Assuming that there are also many patients with fever during simultaneous epidemics, the following measures should be promoted according to the actual situation of each region: strengthening of fever outpatient clinics, strengthening of telephone and online examination services in preparation for cases of overcrowding at fever outpatient clinics, smooth supply of therapeutic drugs, expansion of health follow-up centers, securing of self-examination kits, and strengthening of the consultation system.
• The prefectures will formulate plans to establish systems such as strengthening of outpatient medical care systems in accordance with the actual conditions in each region, and will work to strengthen and prioritize the health care system before the end of November.
• Efforts will be made to provide information to the public and to call for cooperation at outpatient consultations/treatment depending on the risk of becoming severe and prepare antigen qualitative test kits and antipyretic analgesics, etc. from an early stage. It is also necessary to send appropriate messages according to the infection status.
• To prevent infections from becoming severe as far as possible, vaccination against the novel coronavirus as well as the influenza virus should also be promoted among the target population.
• In case the number of infected persons sharply increases and hospitals are overcrowded, or changes in the characteristics of the viruses increase their pathogenicity, measures depending on the situation are required, including requests/calls for residents and business operators to prevent spreading of the infection and to maintain the functions of the medical system, as well as highly effective measures to prevent the spread of infection including behavioral restrictions.

• Deterioration of the accuracy of current surveillance is a concern due to the limited scope of notification, prioritization of notification items, delays in testing and diagnosis/reporting due to many infections, and changes in healthcare-seeking behavior. It is necessary to promptly promote consideration of effective and appropriate surveillance to grasp the epidemic status.
  It is also necessary to continue monitoring the trends of variants through genomic surveillance.

• It is necessary to publicize and recommend effective ventilation methods to prevent insufficient indoor ventilation (how to create airflow considering aerosols, installation of partitions that do not block airflow, etc.).

Re-inspection and implementation of the following basic infection control measures are needed.

• Continue proper wearing of nonwoven masks according to the situation, hand hygiene, thorough ventilation, etc.
• Avoid situations with a high risk of infection, such as the three Cs, congestion, or loud voices.
• Eating and drinking should be done with as few people as possible, and masks should be worn except while eating and drinking.
• People with symptoms such as sore throat, cough, and fever should refrain from going out.
• Refer to guidelines for hospital visits and use of an ambulance.
• Prepare antigen qualitative test kits/antipyretic analgesic at home, etc.
• To reduce the chances of contact as far as possible, it is necessary for measures at the workplace, such as again promoting the use of telework.
• Organizers of events or meetings should fully evaluate the epidemic situation and risk of infection in the area, and consider whether or not to hold the event. If the event is held, measures should be taken to minimize the infection risk.
• Since the risk of infection remains during the shortened period of home care of those who test positive, they should monitor their own physical condition, such as measuring their own temperature, and taking thorough measures against infection when going out. They must also be asked to avoid contact with people who are at risk of severe disease, such as elderly people.
• To allow the minimum necessary outings, such as shopping for groceries, after 24 hours have passed since symptoms have subsided or when there are no symptoms, it is necessary to take voluntary actions to prevent infection, such as wearing a mask when going out, keeping contact with other people at the minimum period of time necessary, and not using public transportation.

It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.

In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to the mucosa, aerosol inhalation, contact infection, etc.).

It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than with the Delta variant. However, analyses to date show that there are more deaths due to infection with the Omicron variant than seasonal influenza. It also seems as if the incidence of pneumonia is higher than that of seasonal influenza, but given the limited data, it needs to be investigated by various analyses.

Concerning the death toll from the outbreak since the end of last year, it is reported that there are many cases in which the novel coronavirus is not the direct cause of death compared to last summer's outbreak, for example, elderly people who have been in a facility for the elderly before the infection are infected but die due to worsening of the underlying disease. There were many cases of serious respiratory failure due to typical viral pneumonia caused by novel coronavirus infection from the beginning of the novel coronavirus outbreak until the Delta variant outbreak. However, during the Omicron variant outbreak, it was reported that diseases other than pneumonia are the main causes of death, such as exacerbation of the underlying disease that was present before hospitalization and the onset of other complications during hospitalization. In the spread of infection this summer, the rate of severe cases decreased compared to the previous outbreak and the ratio of elderly people among hospitalized patients increased compared to last summer's outbreak. Among the deaths during this summer’s outbreak, mechanical ventilation/nasal high flow use rates and steroid prescription rates have decreased compared to the outbreak from the end of last year.

Fatal cases among infected children in whom endogenous death was identified included cases without underlying diseases. Preliminary reports on the results of on-site investigations have stated that it is necessary to pay attention to neurological symptoms such as convulsions and disturbance of consciousness, and other systemic symptoms than respiratory symptoms, such as vomiting and poor oral intake.

According to Japanese data, risk of infection remains until 10 days after onset, and infectivity is high until 7 days after onset. Even after waiting for 5 days, 1/3 of patients are still shedding infectious viruses. On Day 8 (after waiting 7 days), most patients (approximately 85%) had not shed infectious virus, and it was reported that even in those who shed the virus, the amount of virus decreased to one-sixth after 7 days compared to the initial stage.

For infection with the Omicron variant, the preventive effects of a first vaccination against infection and disease onset are markedly reduced. Its preventive effect on hospitalization is reported to be maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing effect, onset-preventing effect, and hospitalization-preventing effect against infection by the Omicron variant, and information on how these vaccine effects are attenuated after a third vaccination has become available. Regarding the fourth vaccination, it has been reported that while the aggravation-preventing effect was not reduced for 6 weeks, the infection-preventing effect lasted only for a short time.

While the BA.5 lineage continues to be mainstream in the world, there are many reports of sublineages of the Omicron variant and recombinants which have characteristic mutations in the spike protein. There are also sublineages for which superiority in an increase in infected patients has been indicated, including the BQ.1 and BQ.1.1 lineages (sublineages of the BA.5.3 lineage), which are frequently reported in Europe and the United States, as well as the XBB lineage (recombinant of the BJ.1 lineage [sublineage of the BA.2.10 lineage] and the BM.1.1.1 lineage [sublineage of the BA.2.75.3 lineage]), which has been reported mainly in India and Singapore. In Europe and the United States, the proportion of BQ.1 and BQ.1.1 lineages is increasing in some countries, and it is expected that the proportion will increase further in the future, but at present, a significant increase in the number of infected persons has not been confirmed. The World Health Organization (WHO), etc., points out that the immune escape of these variants may lead to dominance in increasing the number of infected persons, but the information obtained so far does not suggest that either the infectivity or seriousness of the variants is increasing. It is necessary to continue to collect data and analyze the situation and findings in other countries regarding these characteristics of the new sublineages and recombinants, and to continue monitoring by genome surveillance.

Immunity acquired both from vaccination and natural infection may decline over time. Although the vaccination rate is higher among people in their 60s and older than those in their 20s to 40s, the acquisition of immunity by infection is lower, and there is concern about the spread of infection among elderly people.

Although there are regional differences, the nighttime population has remained almost flat recently. There is concern about increased contact opportunities due to the reactivation of socioeconomic activities toward the end of the year.

In Japan, the BA.5 lineage has largely become mainstream. It is necessary to pay close attention to the strains that have been pointed out to be dominant in the increase in the number of infected persons overseas, such as BQ.1 and BQ.1.1 lineages (sublineages of the BA.5.3 lineage), as the proportion may increase further in the future.

Weather conditions are currently favorable for ventilation, but proper ventilation may be difficult due to a decline in temperature in the days ahead.
In addition, respiratory virus infections tend to increase in winter.

• As for the “vaccine for the Omicron variant," vaccination of all persons aged 12 and over who have completed the first vaccination should proceed.
• Vaccination for the BA.4 and BA.5 lineages has also started. As both vaccines for the BA.1 and the BA.4 and BA.5 lineages are expected to be more effective than the previous vaccines, it is necessary to proceed with vaccination with the vaccine that can be given sooner. As the vaccination interval from the last vaccination was shortened from 5 to 3 months, all eligible persons who wish to receive vaccination will be asked to receive the vaccine for the Omicron variant within this year.
• Those who have not received vaccination will be encouraged to consider getting the initial vaccination as soon as possible.
• For children (ages 5 to 11), booster vaccinations will be promoted along with the initial vaccination.
• The initial vaccination for children (aged 6 months to 4 years) has been approved by the PMDA and positioned as an extraordinary vaccination, and initial vaccination in this age group will proceed.

• Based on the recommendations of the 17th meeting of the Novel Coronavirus Subcommittee, the national and local governments are required to secure a system that enables testing, and further utilize testing.
• Perform frequent tests (about 2 or 3 times a week for facility workers) for workers at facilities for elderly people.
• Establishment of a system for fever outpatients should be further promoted, so that patients with symptoms can self-test using an antigen qualitative test kit, and if the result is positive, they can promptly undergo health observation at a health follow-up center, etc.
• Further promotion of the utilization of antigen qualitative test kits, which have been switched to OTC and are sold on the internet.

• Prefectural governments must take measures to avoid overcrowding of beds and fever outpatient sections with the support of the national government.
• In addition to facilitating the use of available hospital beds and developing temporary medical facilities to supplement hospital beds, making efforts to avoid a shortage of hospital beds and emergency medical care, such as utilization of lodging facilities and resting beds
• Making appropriate adjustments so that patients requiring inpatient treatment can be hospitalized preferentially, performing frequent tests at facilities for elderly people, etc., and further strengthening medical support
• Securing and expanding logistical support hospitals, and improving the hospital turnover rate, such as by dissemination of the standard for early discharge of 4 days, as a rule
• Promotion of effective and less burdensome measures against infection, such as flexible and efficient use of hospital beds through zoning of each hospital room
• Expansion and promotion of fever outpatient services, including the use of online medical care, etc., and further promotion of the development of a “fever outpatient self-examination system”
• Local residents should be informed that they should refrain from visiting an emergency outpatient unit only to receive a precautionary examination without symptoms, according to the actual situation in the region. In addition, in order to respond to concerns and questions at the time of worsening physical conditions, the consultation service by healthcare professionals via telephone should be thoroughly publicized, and this service should also be strengthened.
• Ensuring that workplaces and schools do not require test certificates at the start of medical treatment

• Assuming that there are also many patients with fever during simultaneous epidemics, the following measures should be promoted according to the actual situation of each region: strengthening of fever outpatient clinics, strengthening of telephone and online examination services in preparation for cases of overcrowding at fever outpatient clinics, smooth supply of therapeutic drugs, expansion of health follow-up centers, securing of self-examination kits, and strengthening of the consultation system.
• The prefectures will formulate plans to establish systems such as strengthening of outpatient medical care systems in accordance with the actual conditions in each region.
• Efforts will also be made to provide information to the public and to call for cooperation at outpatient consultations/treatment depending on the risk of becoming severe and prepare antigen qualitative test kits and antipyretic analgesics, etc. from an early stage.
• To prevent the infection of infected patients from becoming severe as far as possible, vaccination against the novel coronavirus as well as the influenza virus should also be promoted among the target population for vaccination.
• In case the number of infected persons sharply increases and hospitals are overcrowded, or changes in the characteristics of the viruses increase their pathogenicity, measures depending on the situation are required, including requests/calls for residents and business operators to prevent spreading of the infection and to maintain the functions of the medical system, as well as highly effective measures to prevent the spread of infection including behavioral restrictions.

• Deterioration of the accuracy of current surveillance is a concern due to the limited scope of notification, prioritization of notification items, delays in testing and diagnosis/reporting due to many infections, and changes in healthcare-seeking behavior. It is necessary to promptly promote consideration of effective and appropriate surveillance to grasp the epidemic status.
  It is also necessary to continue monitoring the trends of variants through genomic surveillance.

• Based on the recommendations of the 17th meeting of the Novel Coronavirus Subcommittee, it is necessary to publicize and recommend effective ventilation methods to prevent insufficient indoor ventilation (how to create airflow considering aerosols, installation of partitions that do not block airflow, etc.).

Re-inspection and implementation of the following basic infection control measures are needed.

• Continue proper wearing of nonwoven masks according to the situation, hand hygiene, thorough ventilation, etc.
• Avoid situations with a high risk of infection, such as the three Cs, congestion, or loud voices.
• Eating and drinking should be done with as few people as possible, and masks should be worn except while eating and drinking.
• People with symptoms such as sore throat, cough, and fever should refrain from going out.
• Refer to guidelines for hospital visits and use of an ambulance.
• Prepare antigen qualitative test kits/antipyretic analgesic at home, etc.
• To reduce the chances of contact as far as possible, it is necessary for measures at the workplace, such as again promoting the use of telework.
• Organizers of events or meetings should fully evaluate the epidemic situation and risk of infection in the area and consider whether or not to hold the event. If the event is held, measures should be taken to minimize the infection risk.
• Since the risk of infection remains during the shortened period of home care of those who test positive, they should monitor their own physical condition, such as measuring their own temperature, and taking thorough measures against infection when going out. They must also be asked to avoid contact with people who are at risk of severe disease, such as elderly people.
• To allow the minimum necessary outings, such as shopping for groceries, after 24 hours have passed since symptoms have subsided or when there are no symptoms, it is necessary to take voluntary actions to prevent infection, such as wearing a mask when going out, keeping contact with other people at the minimum period of time necessary, and not using public transportation.

It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.

In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to the mucosa, aerosol inhalation, contact infection, etc.).

It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than with the Delta variant. However, analyses to date show that there are more deaths due to infection with the Omicron variant than seasonal influenza. It also seems as if the incidence of pneumonia is higher than that of seasonal influenza, but given the limited data, it needs to be investigated by various analyses.

Concerning the death toll from the previous outbreak, it is reported that there are many cases in which the novel coronavirus infection is not the direct cause of death compared to last summer's outbreak, for example, elderly people who have been in a facility for the elderly before the infection are infected but die due to worsening of the underlying disease. There were many cases of serious respiratory failure due to typical viral pneumonia caused by novel coronavirus infection from the beginning of the novel coronavirus outbreak until the Delta variant outbreak. However, during the Omicron variant outbreak, it was reported that other diseases than pneumonia are the main causes of death, such as exacerbation of the underlying disease that was present before hospitalization and the onset of other complications during hospitalization.

In the current spread of infection, the rate of severe cases has decreased compared to the previous outbreak and the ratio of elderly people among hospitalized patients has increased compared to last summer's outbreak. Among the deaths during this outbreak, mechanical ventilation/nasal high flow use rates and steroid prescription rates have decreased compared to the previous outbreak.
Among fatal cases in which endogenous death was identified in infected children, cases without underlying diseases were also found. Preliminary reports on the results of on-site investigations have stated that it is necessary to pay attention to neurological symptoms such as convulsions and disturbance of consciousness, and systemic symptoms other than respiratory symptoms such as vomiting and poor oral intake.

According to Japanese data, risk of infection remains until 10 days after onset, and infectivity is high until 7 days after onset. Even after waiting for 5 days, 1/3 of patients are still shedding infectious viruses. On Day 8 (after waiting 7 days), most patients (approximately 85%) had not shed infectious virus, and it was reported that even in those who shed the virus, the amount of virus decreased to one-sixth after 7 days compared to the initial stage.

For infection with the Omicron variant, the preventive effects of a first vaccination against infection and disease onset are markedly reduced. Its preventive effect on hospitalization is reported to be maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing effect, onset-preventing effect, and hospitalization-preventing effect against infection by the Omicron variant, and information on how these vaccine effects are attenuated after a third vaccination has become available. Regarding the fourth vaccination, it has been reported that while the aggravation-preventing effect was not reduced for 6 weeks, the infection-preventing effect lasted only for a short time.

While the BA.5 lineage continues to be mainstream in the world, there are many reports of sublineages of the Omicron variant and recombinants which have characteristic mutations in the spike protein. There are also sublineages for which superiority in an increase in infected patients has been indicated, including the BQ.1 and BQ.1.1 lineages (sublineages of the BA.5.3 lineage), which are frequently reported in Europe and the United States, as well as the XBB lineage (recombinant of the BJ.1 lineage [sublineage of the BA.2.10 lineage] and the BM.1.1.1 lineage [sublineage of the BA.2.75.3 lineage]), which has been reported mainly in India and Singapore. In Europe and the United States, the proportion of BQ.1 and BQ.1.1 lineages is increasing in some countries, and it is expected that the proportion will increase further in the future, but at present, a significant increase in the number of infected persons has not been confirmed. The World Health Organization (WHO), etc., points out that the immune escape of these variants may lead to dominance in increasing the number of infected persons, but the information obtained so far does not suggest that either the infectivity or seriousness of the variants is increasing. It is necessary to continue to collect data and analyze the situation and findings in other countries regarding these characteristics of the new sublineages and recombinants, and to continue monitoring by genome surveillance.

Immunity acquired from vaccination and natural infection may decline over time. Although the vaccination rate is higher among people in their 60s and older than those in their 20s to 40s, the acquisition of immunity by infection is lower, and there is concern about the spread of infection among elderly people.

The nighttime population is increasing in many regions including Hokkaido, Tokyo, Aichi, Osaka, and Okinawa. There is also concern about increased contact opportunities due to the reactivation of socioeconomic activities toward the end of the year.

In Japan, the BA.5 lineage has largely become mainstream, and is replacing others. At present, there is not a trend toward further replacement by another lineage.

Weather conditions are currently favorable for ventilation, but proper ventilation may be difficult on days with a low temperature or bad weather such as heavy rainfall.
Respiratory virus infections tend to increase in winter.

• As for the “vaccine for the Omicron variant," vaccination of all persons aged 12 and over who have completed the first vaccination should proceed.
• Vaccination for the BA.4 and BA.5 lineages has also started. As both vaccines for the BA.1 and for the BA.4 and BA.5 lineages are expected to be more effective than the previous vaccines, it is necessary to proceed with vaccination with the vaccine that can be given sooner. As the vaccination interval from the last vaccination was shortened from 5 months to 3 months, all eligible persons will be asked to receive the vaccine for the Omicron variant within this year.
• Those who have not received vaccination will be encouraged to consider getting the initial vaccination as soon as possible.
• For children (ages 5 to 11), booster vaccinations will be promoted along with the initial vaccination.
• The initial vaccination for children (aged 6 months to 4 years) has been approved by the PMDA and positioned as an extraordinary vaccination, and initial vaccination in this age group will proceed.

• Based on the recommendations of the 17th meeting of the Novel Coronavirus Subcommittee, the national and local governments are required to secure a system that enables testing, and further utilize testing.
• Perform frequent tests (about 2 or 3 times a week for facility workers) for workers at facilities for elderly people.
• Establishment of a system for fever outpatients should be further promoted, so that patients with symptoms can self-test using an antigen qualitative test kit, and if the result is positive, they can promptly undergo health observation at a health follow-up center, etc.
• Further promotion of the utilization of antigen qualitative test kits, which have been switched to OTC and are sold on the internet.

• Prefectural governments must take measures to avoid overcrowding of beds and fever outpatient sections with the support of the national government.
• In addition to facilitating the use of available hospital beds and developing temporary medical facilities to supplement hospital beds, making efforts to avoid a shortage of hospital beds and emergency medical care, such as utilization of lodging facilities and resting beds
• Making appropriate adjustments so that patients requiring inpatient treatment can be hospitalized preferentially, performing frequent tests at facilities for elderly people, etc., and further strengthening medical support
• Securing and expanding logistical support hospitals, and improving the hospital turnover rate, such as by dissemination of the standard for early discharge of 4 days, as a rule
• Promotion of effective and less burdensome measures against infection, such as flexible and efficient use of hospital beds through zoning of each hospital room
• Expansion and promotion of fever outpatient services, including the use of online medical care, etc., and further promotion of the development of a “fever outpatient self-examination system”
• Local residents should be informed that they should refrain from visiting an emergency outpatient unit only to receive a precautionary examination without symptoms, according to the actual situation in the region. In addition, in order to respond to concerns and questions at the time of worsening physical conditions, the consultation service by healthcare professionals via telephone should be thoroughly publicized, and this service should also be strengthened.
• Ensuring that workplaces and schools do not require test certificates at the start of medical treatment

• Assuming that there are many patients with fever during simultaneous epidemics, the following measures should be promoted according to the actual situation in each region: strengthening of fever outpatient clinics, strengthening of telephone and online examination services in preparation for cases of overcrowding at fever outpatient clinics, smooth supply of therapeutic drugs, expansion of health follow-up centers, securing of self-examination kits, and strengthening of the consultation system.
• The prefectures will formulate plans to establish systems such as strengthening of outpatient medical care systems in accordance with the actual conditions in each region.
• In addition, efforts will be made to provide information to the public and to call for cooperation at clinic visits/treatment according to the risk of aggravation.
• To prevent the infection of infected patients from becoming severe as far as possible, vaccination against the novel coronavirus as well as the influenza virus should also be promoted among the target population for vaccination.
• In case the number of infected persons sharply increases and hospitals are overcrowded, or changes in the characteristics of the viruses increase their pathogenicity, measures depending on the situation are required, including requests/calls for residents and business operators to prevent spreading of the infection and to maintain the functions of the medical system, as well as highly effective measures to prevent the spread of infection including behavioral restrictions.

• Deterioration of the accuracy of current surveillance is a concern due to the limited scope of notification, prioritization of notification items, delays in testing and diagnosis/reporting due to many cases of infection, and changes in healthcare-seeking behavior. It is necessary to promptly develop an effective and appropriate surveillance program to grasp the epidemic status.
  It is also necessary to continue monitoring the trends of variants through genomic surveillance.

• Based on the recommendations of the 17th meeting of the Novel Coronavirus Subcommittee, it is necessary to publicize and recommend effective ventilation methods to prevent insufficient indoor ventilation (how to create airflow considering aerosols, installation of partitions that do not block airflow, etc.).

• Re-inspection and implementation of the following basic infection control measures are needed.
• Continue proper wearing of nonwoven masks according to the situation, hand hygiene, thorough ventilation, etc.
• Avoid situations with a high risk of infection, such as the three Cs, congestion, or loud voices.
• Eating and drinking should be done with as few people as possible, and masks should be worn except while eating and drinking.
• People with symptoms such as sore throat, cough, and fever should refrain from going out.
• Refer to guidelines for hospital visits and use of an ambulance.
• To reduce the chances of contact as far as possible, it is necessary for measures at the workplace, such as again promoting the use of telework.
• Organizers of events or meetings should fully evaluate the epidemic situation and risk of infection in the area, and consider whether or not to hold the event. If the event is held, measures should be taken to minimize the infection risk.
• Since a risk of infection remains during the shortened period of home care of patients who test positive, patients should monitor their own physical condition, such as measuring their temperature, and take thorough measures against infection when going out.
  They must also be asked to avoid contact with people who are at risk of severe disease, such as elderly people.
• To allow the minimum necessary outings, such as shopping for groceries, after 24 hours have passed since symptoms have subsided or when there are no symptoms, it is necessary to take voluntary actions to prevent infection, such as wearing a mask when going out, keeping contact with other people at the minimum period of time necessary, and not using public transportation.

It has been confirmed that compared to the Delta variant, the generation time has shortened to approximately 2 days (it is approximately 5 days for Delta). The doubling time and incubation period have also shortened, the risk of re-infection and secondary infection after infection has increased, and the speed of infection spread is very fast. According to the reported data, pre-symptomatic transmission has probably occurred to some extent as with the previous strains.

In Japan, many cases of infection have occurred through the same opportunities as before (spending time indoors in locations with inadequate ventilation, eating and drinking, etc.), and infection is considered to have occurred via the same routes as before (droplets adhering to mucosa, aerosol inhalation, contact infection, etc.).

It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than the Delta variant. However, analyses to date show that the fatality due to infection with the Omicron variant is higher than that due to seasonal influenza. It is also suggested that the incidence of pneumonia is higher than that of seasonal influenza, but given the limited data, it needs to be investigated by various analyses.

Concerning the death toll from the previous outbreak, it is reported that there are many cases in which the novel coronavirus infection is not the direct cause of death compared to last summer's outbreak, for example, elderly people who have been in a facility for the elderly before the infection are infected but die due to worsening of the underlying disease. There were many cases of serious respiratory failure due to typical viral pneumonia caused by novel coronavirus infection from the beginning of the novel coronavirus outbreak until the Delta variant outbreak. However, during the Omicron variant outbreak, it was reported that other diseases than pneumonia are the main causes of death, such as exacerbation of the underlying disease that was present before hospitalization and the onset of other complications during hospitalization.

In the current spread of infection, the rate of severe cases has decreased compared to the previous outbreak and the ratio of elderly people among hospitalized patients has increased compared to last summer's outbreak. Among the deaths during this outbreak, mechanical ventilation/nasal high flow use rates and steroid prescription rates have decreased compared to the previous outbreak.
Fatal cases among infected children in whom endogenous death was identified included cases without underlying diseases. Preliminary reports on the results of on-site investigations have stated that it is necessary to pay attention to neurological symptoms such as convulsions and disturbance of consciousness, and other systemic symptoms than respiratory symptoms, such as vomiting and poor oral intake.

According to the Japanese data, the risk of spreading infection remains until 10 days after onset, and infectivity is high until 7 days after onset. Even after isolation for 5 days, 1/3 of patients are still shedding infectious viruses. On Day 8 (after isolation for 7 days), most patients (approximately 85%) did not shed infectious viruses, and it was reported that even if patients shed the virus, the amount of virus decreased to one-sixth that in the initial stage of onset after 7 days.

Concerning infection with the Omicron variant, the preventive effects of the initial immunization against infection and disease onset are markedly reduced. Its hospitalization-preventing effect is reported to be maintained at a certain level for the first 6 months, but subsequently decreases to 50% or less. On the other hand, it has been reported overseas that a third vaccination restores the infection-preventing effect, onset-preventing effect, and hospitalization-preventing effect against infection by the Omicron variant, and information on how these vaccine effects are attenuated after a third vaccination has become available. Regarding the fourth vaccination, it has been reported that while the aggravation-preventing effect was not reduced for 6 weeks, the infection-preventing effect lasted only for a short time.

While the BA.5 lineage continues to be mainstream in the world, there are many reports of sublineages of the Omicron variant and recombinants with characteristic mutations in the spike protein. There are also sublineages for which superiority in an increase in infected patients has been indicated, including the BQ.1 and BQ.1.1 lineages (sublineages of the BA.5.3 lineage), which are frequently reported in Europe and the United States, as well as the XBB lineage (recombinant of the BJ.1 lineage [sublineages of the BA.2.10 lineage] and the BM.1.1.1 lineage [sublineages of the BA.2.75.3 lineage]), which has been reported mainly in India and Singapore. In Europe and the United States, there is concern that the proportion of the BQ.1 and BQ.1.1 lineages will increase in the future. However, no clear findings on the infectivity and severity of these variants have been obtained.

It is necessary to continue to collect and analyze the situation and findings in other countries regarding these characteristics of the new sublineages and recombinants, and to continue monitoring by genome surveillance.