国立感染症研究所

121st Meeting of the COVID-19 Advisory Board of the Ministry of Health, Labour and Welfare (April 19, 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 46 per 100,000 of the population in the last week, showing a gradually increasing trend with a ratio of this week to last week of 1.06.
  It is necessary to pay attention to the impact of increased opportunities for contact, attenuation of immunity, and replacement by variant strains on the infection status.
• The numbers of severe patients and deaths remain flat, and the use rate of beds is at a low level nationwide.

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 Apr. 18 at 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 the announcement on Apr. 14.

<Changes in the number of new cases of infection and comparison to the previous week (nationwide) >

Infection status and future outlook

Infection status

• The number of new cases of infection has gradually been increasing after a nationwide halt. On the other hand, the level continues to be lower than before the spread of infection in the summer last year (2022).
• Regarding the number of new cases of infection by region, in Hokkaido, the Hokuriku-Koshinetsu region, and Okinawa, the number per population is higher than the national average. Meanwhile, in the Tokai, Shikoku, and Kyushu regions, the number is lower than the average. In addition, the number of cases of mass infection in facilities for elderly people and medical institutions has leveled off.
• Seen by age group, the number of new cases of infection has recently increased in teens and younger people nationwide, although the number has also increased in people in their 20s in some large cities such as Tokyo and Osaka.
• The numbers of severe patients and deaths remain flat nationwide. With the spread of infection this winter, the proportion of elderly patients in their 80s and older among newly infected patients tended to increase, compared to that during the spread of infection in the summer last year (2022).
• 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.
• Regarding seasonal influenza, at the time of the announcement last weekend, the weekly number of reports per fixed-point medical institution was decreasing nationwide, and is far below the advisory level.

Future outlook

• Attention should be paid to the future infection status because the number of new cases of infection may remain flat or continue to show a gradually increasing trend nationwide, although it may differ among regions. It is also necessary to pay attention to the future impact of increased opportunities for contact, the attenuation of immunity, and an increase in the proportion of strains that can escape the immune system, on the infection status.
• In light of the situation the past 2 years, it is considered that the infection will spread after the consecutive holidays in May, that it will decrease once and then spread again in the summer.
• Although seasonal influenza is still at the advisory level in some regions, it is expected to decrease further based on past trends.

Factors that increase and suppress infection

1. [Immunity as a result of vaccination and infection]

   With the promotion of vaccination and natural infection, it is considered that the proportion of immune carriers against the Omicron variant (BA.5 and BQ1.1), which has shown an increase in each age group, will decrease over time in the future.

2. [Contact status]

   There are many regions where the nighttime population is currently decreasing compared to the level at the start of the new fiscal year. In the future, however, opportunities for contact is expected to increase due to the consecutive holidays in May.

3. [Epidemic strain]

   In Japan, the BA.5 lineage, including the BQ.1 lineage, was mainstream, but its proportion has tended to decrease since around March. On the other hand, the proportions of the XBB.1.5 lineage, which is frequently reported in the United States, the XBB.1.9 lineage, which is frequently reported in Europe, and the XBB lineage including the XBB.1.16 lineage, which is frequently reported in India, are on the rise. Since the number of registered variant strains is decreasing as the number of infected people in Japan decreases, caution is required when considering the proportion of variant strains.

4. [Climate/Seasonal Factors]

   With the temperature rising now, the climate conditions will facilitate ventilation. It is thought that a reduction of the amount of time spent indoors has a certain effect on suppressing infection; however, it should be noted that the infection may spread during this period.

Situation of the medical care provision system

• The use rate of beds is at a low level below 10% in most regions. The use rate of beds for severe patients is also low nationwide.
• The number of patients receiving treatment in nursing care facilities has continued to decrease.
• Regarding emergency medical care, the number of cases where emergency transportation is difficult remains flat nationwide, but attention should continuously be paid to the future trend of the number of cases where emergency transportation is difficult and securing of 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, the government decided on March 10 this year to make necessary revisions to various policies and measures that have been taken, such as the medical care system, response to facilities for the elderly, and public financial support for patients.
• 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 5 and older who have completed the first vaccination should proceed.
   • All eligible persons who wish to receive vaccination will be encouraged 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 (aged 5 to 11 years), the initial vaccination and additional vaccination with the vaccine for the Omicron variant will be promoted. For children (aged 6 months to 4 years), the initial vaccination will be promoted.
   • Vaccination in FY 2023 will be promoted (vaccination will be given to all eligible persons aged 5 years and older in autumn and winter, and vaccination will be given to elderly people and those at high risk of aggravation in spring and summer, without waiting until autumn or winter).
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. Effective ventilation
   • It is necessary to publicize and recommend effective indoor ventilation methods (such as how to create airflow considering aerosols, the installation of partitions that do not block airflow, etc.).
4. 4. Securing a medical care provision system
   • With support of the national government, local governments continue to take measures to avoid overcrowding of hospital beds, fever clinics, etc.
   • 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.
   • 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.
   • In response to the government's decision on March 10 this year, with the change in positioning as a Class V Infectious Disease, encourage medical facilities that have been responding to the new coronavirus infection to continue to respond, and start efforts to encourage new medical facilities to participate.
   • Maintenance and expansion of responding medical institutions through review of infection control measures, support for maintenance of facilities, clarification of the obligation to provide treatment, and dissemination of easy-to-understand educational materials on infection control and medical treatment policies
   • In each prefecture, until the expansion of infection in the next winter a transition plan up to the end of September will be formulated in April, with contents such as the acceptance of patients with mild disease by new medical institutions, and the coordination of hospitalization among medical institutions.
5. 5. Response to simultaneous epidemics of COVID-19 and seasonal influenza
   • The following efforts should be promoted according to the actual situation in each region: fever outpatient clinics, telephone consultations/telemedicine, health follow-up centers, self-test kits, consultation system, and 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 regarding antipyretic analgesics, etc.
   • 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 send appropriate messages to the public depending on the infection status. 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.
6. 6. Surveillance and risk assessment, etc.
   • After the position of COVID-19 under the Infectious Disease Act is changed on May 8 this year (2023), preparations will be made in cooperation with local governments to perform a stratified analysis through continued seroepidemiologic surveys, sewage surveillance studies, etc. to grasp and publish data such as the numbers of infected patients, hospitalized patients, and deaths. Monitoring of the trends of variant strains will also be continued through genome surveillance.
   • Regarding the risk assessment of COVID-19, it is necessary to continue evaluation of the pathogenicity, infectivity, mutations, etc.
7. 7. Quarantine measures
   • Regarding temporary measures for people entering from China after December 30th last year, sample tests at entry which have been conducted for some people entering Japan since March 1 this year will be continued. From April 5th this year, instead of submission of a negative certificate, those who enter from China by mainland flight will be required to submit either a negative certificate or a certificate of vaccination (three times), considering the situation of infections in Japan and overseas, knowledge obtained through temporary measures, and the status of quarantine measures in G7 countries.
   • Along with the end of quarantine measures scheduled for May 8 this year (2023), Infection Genome Surveillance (provisional name) will start on the same day to monitor the influx of new infectious diseases, even in ordinary times.
8. 8. Re-inspection and implementation of basic infection control measures

   Everyone must take the following basic precautions from the perspective of being aware of the epidemic of infectious disease in the community, protecting ourselves from infectious disease, and protecting people close to us as well as society from infectious disease, especially the elderly.

   • If feeling unwell or having symptoms, do not overdo it, and be treated at home or see a doctor.
   • Hand hygiene such as hand washing as a daily habit
   • Wearing a mask and practicing cough etiquette according to the situation
   • Understanding and practicing lifestyle habits such as moderate exercise and diet
   • Enforcement of ventilation, and avoiding crowded places, close contact, and closed spaces (the 3 Cs)
   • Make efforts such as promoting the use of telework in the workplace.
   • From May 8 this year, the government will not uniformly request the use of basic infection control measures but will respect the independent choice of individuals and leave it to their judgment.
   • Concerning the period of home care for people who test positive, they should monitor their own physical condition by such means as checking their body temperature and take thorough infection control measures when going out. They are also requested to avoid contact with people who are at risk of severe disease, such as elderly people. From May 8 this year (2023), it will be recommended that they refrain from going out for 5 days after the onset of disease and 24 hours after the alleviation of symptoms. It will also be recommended that they wear a mask and avoid contact with high-risk people until 10 days have passed from then.
   • 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 also considered to have occurred via droplets adhering to 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 or aggravation than with the Delta variant. To evaluate COVID-19, including the Omicron variant, it is necessary to assess not only the severity as a disease but also the transmissibility and the impact on medical care and society.

   Concerning the death toll during the spread of infection from the end of 2021, it has been reported that COVID-19 was not the direct cause of death in quite a number of cases, compared to that during the spread of infection in the summer of 2021; for example, there were deaths due to the worsening of underlying diseases after infection with the novel coronavirus in elderly people who had been living in a facility for elderly people since before the infection. 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 Delta variant epidemic. However, during the Omicron variant epidemic, it was reported that other diseases than pneumonia became the main cause of death, such as the exacerbation of underlying disease that had been present before hospitalization and the onset of other complications during hospitalization.

   During the spread of infection last summer, a decrease in the rate of severe cases and an increase in the proportion of elderly people among hospitalized patients were seen, as had been seen previously, compared to the spread of infection in the summer of 2021. In addition, compared to the situation during the spread of infection since the end of 2021, the rates of mechanical ventilation/nasal high flow use and steroid prescription among the number of deaths associated with the spread of infection was lower during the summer of 2022.

   Among the fatal cases of infected children who died of endogenous factors, there were some cases without any underlying diseases. 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 as well as systemic symptoms such as vomiting and poor oral intake besides 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 factors other than COVID-19. Regarding the situation of handling known coronavirus-positive corpses, the number of cases reported monthly was the highest in December last year (2022). The proportion of deaths due to COVID-19 was approximately 30% of all deaths.

4. [Virus shedding period]

   Japanese data suggest that infectious viruses are expelled in the period from 2 days before the onset of symptoms to 7-10 days after the onset, and that the mean amount of expelled infectious viruses is very high in the first 3 days after the onset of symptoms and greatly decreases to one-twentieth to one-fiftieth the amount on the day of onset after 5 days have passed, approaching the detection limit, although there are individual differences.

5. [Vaccine effects]

   Concerning conventional vaccines, the infection and disease onset prevention effects of the first vaccination against the Omicron variant have been 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 for 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]

   The proportion of the BA.5 lineage, which was the mainstream worldwide, is declining, and on the other hand, the proportion of the XBB lineage (a recombinant of the BJ.1 lineage [a sublineage of the BA.2.10 lineage] and the BM.1.1.1 lineage [a sublineage of the BA.2.75.3 lineage]), including the XBB.1.5 lineage, is increasing currently. The proportion of the XBB.1.5 lineage, the XBB.1.9 lineage, and the XBB.1.16 lineage (all of them include sublineages) is increasing in the United States, Europe, and India, respectively. The severity of disease caused by the XBB.1.5 lineage is not higher than that caused by the BQ.1 lineage, but its clinical picture and epidemiological findings are otherwise insufficient. The clinical picture and epidemiological findings are also insufficient regarding the XBB.1.9 lineage and the XBB.1.16 lineage. It is therefore necessary to continue collecting and analyzing data on overseas situations and to continue monitoring through genome surveillance. Caution should be exercised when considering the proportion of variant strains because the number of registered variant strains is decreasing as the number of infected people decreases worldwide.

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