国立感染症研究所

116th Meeting of the COVID-19 Advisory Board of the Ministry of Health, Labour and Welfare (February 8, 2023) Material 1

 

Evaluation of the latest infection status, etc.

Overview of the infection status, etc.

  • The number of new cases of infection nationwide was approximately 214 per 100,000 of the population in the last week, showing a continuous decreasing trend with a ratio of this week to last week of 0.72.
    It is necessary to pay attention to the future impact of attenuation of immunity and replacement by variant strains on the infection status.
  • The use rate of beds has been decreasing nationwide, and the number of deaths and emergency cases that are difficult to transport have also continued to decrease although the numbers remain high.

Reference: Local trend

* The number of new cases of infection is an approximate figure per 100,000 of the population, as the total for the current week, which is the reported number in HER-SYS as of Feb. 7, 00:00 AM (the same time point is used for the ratio to the previous week), and the use rate of beds is the secured bed use rate as of the time of writing this document on Feb. 7.

Infection status and future outlook

Infection status
  • The number of new cases of infection shows a continuous decreasing trend nationwide, and the ratio to the previous week remains below 1.0 in all prefectures.
  • Regarding the number of new cases of infection by region, in the Tokai, Chugoku, Shikoku, and Kyushu regions, the number per population is higher than the national average. Meanwhile, in the Hokkaido, Tohoku and Kanto regions and Okinawa, the number is lower than the average. However, the regional differences are also decreasing as the infection status improves. In addition, there is a decreasing trend in mass infections in facilities for elderly people, medical institutions, etc.
  • The number of new cases of infection nationwide by age group shows a decreasing trend in all age groups. A decrease in the number is significant even in the group of those under 10 years old that accounts for a large proportion of new cases of infection.
  • The number of severe cases has been decreasing nationwide, and the number of deaths has also continued to decrease, although the number remains high. With the recent expansion of infection, the proportion of elderly patients in their 80s and older among newly infected patients shows an increasing trend compared to that at the time of expansion of the infection the last summer. Attention should continuously be paid because the underlying diseases tend to deteriorate in winter.
  • As the reports of deaths among children since January 2022 suggest, attention must be paid to the occurrence of severe cases and deaths as well as the number of hospitalized children associated with an increase in the number of infected children.
  • The incidence of seasonal influenza is lower than during the same period in usual years, but higher than during the same period in the previous two years. At the time of the announcement last weekend, the number of cases reported weekly per fixed-point medical institution exceeded 10 nationwide, and the number exceeded 30 in Okinawa. Both numbers have reached a warning level. Nationwide, the number is still on an increasing trend, although the increase is smaller than in the previous week.
Future outlook
  • Regarding the future infection status, it is expected to show a continuous decreasing trend nationwide, despite regional differences and uncertainty, based on the epi curves and short-term forecasts nationwide and in large cities. It is necessary to pay attention to the future impact of the attenuation of immunity and an increase in the proportion of strains with the ability to escape the immune system on the infection status.
  • Concerning the level of seasonal influenza, an increase in infection cases is expected to continue based on past trends, although the increase is narrowing. Attention needs to be paid to simultaneous infection of influenza and COVID-19.
Factors that increase and suppress infection
  1. [Immunity as a result of vaccination and infection]

    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 already have declined in elderly people.

  2. [Contact situation]

    The nighttime population has recently increased in many large cities but has decreased in some regions, showing regional differences.

  3. [Epidemic strains]

    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 an enhanced ability 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.

  4. [Climatic and seasonal factors]

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

Situation of the medical care provision system
  • The use rate of beds has been decreasing nationwide and is below 50% in almost all regions. The use rate of beds for severe cases has also been declining in many regions.
  • The number of patients receiving treatment in nursing care facilities has been decreasing.
  • As for emergency medical care, while the medical care system is usually overloaded in winter, the number of cases having difficulty with emergency transportation remains at a high level nationwide but shows a continuous decreasing trend. Attention should continuously be paid to the future trend of the number of cases having difficulty with emergency transportation and securing a system to provide emergency medical care.

Measures to be taken

Basic concepts
  • Unless we face special circumstances such as the emergence of a variant with a pathogenicity greatly different from that of the Omicron variant, COVID-19 shall be positioned as a Class V Infectious Disease instead of a Novel Influenza Infection, etc. under the Infectious Disease Act from May 8 this year (2023). In association with this, various policies and measures taken will be reviewed.
  • Meanwhile, it is necessary to continue efforts to strengthen and focus the healthcare system to provide appropriate medical care for elderly people and those at high risk of aggravation, even with limited medical resources.
    Each citizen will be asked to take voluntary actions to prevent infection to protect those at high risk of aggravation, such as elderly people, and to ensure regular medical care.
  1. 1. Further promotion of vaccination
    • 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.
  2. 2. Use of tests
    • The national and local governments are required to secure a system that enables testing, and should utilize testing.
    • Perform frequent tests (about 2 or 3 times a week for facility workers) for workers at facilities for elderly people.
    • Promote the establishment of a system for fever outpatients, whereby 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.
    • Promote the utilization of antigen qualitative test kits, which have been switched to OTC and are sold on the internet.
  3. 3. Quarantine measures
    • The COVID-19 situation in China is rapidly worsening, making it difficult to grasp the details. 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.
  4. 4. Securing a medical care provision system
    • In winter, it is also the time when the number of patients with other diseases than COVID-19 increase. With the support of the national government, prefectural governments must take measures mainly to avoid overcrowding of hospital beds and fever outpatient clinics.
    • Maintain the total number of beds required for patients infected with COVID-19 based on the bed securing plan. 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.).
    • Take immediate responses such as securing beds, and make efforts to avoid being overwhelmed concerning the number of hospital beds and emergency medical care by using lodging facilities and resting beds, for example.
    • Make appropriate adjustments 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). Implement frequent examinations at facilities for elderly people and others. Further strengthen 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
  5. 5. Response to simultaneous epidemics of COVID-19 and seasonal influenza
    • As measures for people 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/telemedicine, expansion of health follow-up centers, securing of self-test kits, strengthening of the consultation system, and prevention of overcrowded emergency medical care.
      Smooth supply of medications including oral drugs prescribed after confirmation of the indication by physicians will be promoted. 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. People at low risk of aggravation will be encouraged to use a self-test kit or local follow-up center. 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.
  6. 6. Surveillance and risk assessment, etc.
    • 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.
  7. 7. Effective ventilation
    • 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.
  8. 8. Re-inspection and implementation of basic infection control

    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.
    • Make efforts such as promoting the use of telework in the workplace.
    • The organizers of events or meetings should examine and evaluate the epidemic status in the concerned region as well as the risk of infection, and then take measures to reduce the risk.
    • Test-positive persons on home care should monitor their own physical condition by such means as checking their body 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, keeping contact with other people at the minimum period of time possible, and not using public transportation.
<< Reference: Findings on the characteristics of the Omicron variant and its sublineages >>
  1. [Infectivity/transmissibility]

    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.

  2. [Place/route of infection]

    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.).

  3. [Severity, 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. Regarding the situation of handling dead bodies known to be coronavirus positive, the number of cases reported monthly has been the highest during last December. The proportion of deaths due to COVID-19 has recently reached approximately 30% of all deaths. The local governments are developing outpatient medical care and health follow-up systems including medical institutions that provide care or perform examinations. It is important to continuously endeavor to provide the necessary medical care to home care patients.

  4. [Virus shedding period]

    According to Japanese data, the risk of infection remains until 10 days after the onset, and infectivity is high until 7 days after the 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.

  5. [Vaccine effects]

    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.

  6. [Sublineages of the Omicron variant]

    While the BA.5 lineage continues to be mainstream in the world, there are reports of sublineages of the Omicron variant and recombinants of them with characteristic mutations in the spike protein. They include sublineages of which a predominance in the increasing number of infected patients has been indicated, such as the BQ.1 lineage (sublineage of the BA.5.3 lineage), 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]), and the CH.1.1 lineage (sublineage of the BA.2.75.3 lineage). The proportion of the BQ.1 lineage has increased in Europe, and it 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.

Figures (Number of new infections reported etc.) (PDF)

 

Copyright 1998 National Institute of Infectious Diseases, Japan

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