国立感染症研究所

104th Meeting of the COVID-19 Advisory Board of the Ministry of Health, Labour and Welfare (October 26, 2022) Material 1

Evaluation of the latest infection status, etc.

Overview of the infection status

• Nationwide, the number of new cases of infection (by date of report) was approximately 191 per 100,000 in the current week, and the ratio to the previous week was 0.96. The number of new cases of infection increased in the previous week, but it remained at the same level in the current week. We need to carefully watch the future trend of infection.
  It is also necessary to pay attention to the future impact of increased contact opportunities due to the reactivation of socioeconomic activities on the infection status.
• On the other hand, the use rate of beds is at a low level, while the number of severe patients and deaths has stopped decreasing.

Reference: Local trends

* The number of new cases of infection is an approximate figure per 100,000 as the total for the current week, which is the reported number in HER-SYS as of Oct 25, 00:00 AM (same time point for the ratio to the previous week), and the use rate of beds is a figure as of the writing of this document on Oct 25.

Infection status and future outlook

Infection status

• Nationwide, the number of new cases of infection increased in the previous week, but it remained at the same level in the current week. We need to carefully watch the future trend of infection.
• There are regional differences in the current status of infection, with a significant increase in the Hokkaido, Tohoku, Hokuriku-Koshinetsu, and Chugoku regions, but the number of cases of infection per 100,000 people in the Tokyo metropolitan area and Kyushu/Okinawa is lower than the nationwide number. There are also still mass infections in some facilities for elderly people and medical institutions.
• The number of new cases of infection per population in each age group is higher in younger age groups including teens. The number of new cases of infection among teens is also increasing in regions where the number of new cases of infection is increasing. The number of new cases of infection among elderly people slightly increased, but the numbers of severe patients and deaths stopped decreasing.
• As the provisional report of deaths among children since January this year suggests, attention must be paid to the occurrence of severe cases and deaths associated with an increase in the number of infected children.

Future outlook

• Regarding the future infection status, the number of cases of infection may remain at the same level or continue to increase despite regional differences and uncertainty, based on the short-term forecast in large cities. It is also necessary to pay attention to the future impact of increased contact opportunities due to the reactivation of socioeconomic activities on the infection status.
• Based on the trends of the past two years, there are concerns that the spread of the novel coronavirus infection may start earlier this winter.
  There is also concern that the seasonal influenza epidemic may start earlier than usual, and that these two may occur simultaneously, although the number of cases of seasonal influenza is currently low.

Factors that increase and suppress infection

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

   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.

2. [Contact patterns]

   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.

3. [Epidemic strain]

   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.

4. [Climatic and seasonal factors]

   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.

Situation of the medical care provision system

• Nationwide, the use rate of beds is at a low level below 30% in most regions. The use rate of beds for severe cases is also at a low level, but we need to watch for effects associated with an increase in the number of new cases of infection in the future.
• In the field of nursing care, patients are being treated in facilities and infection is seen among elderly people and workers.
• Cases of problems with emergency transportation remain on the same level nationwide both for suspected non-COVID-19 cases and suspected COVID-19 cases.

Measures to be taken

Basic concepts

• To prepare for re-spreading of the novel coronavirus infection and simultaneous seasonal influenza epidemics, measures to strengthen and focus the healthcare system should be taken for limited medical resources to provide appropriate medical care to elderly people and persons at risk of aggravation.
• Each citizen will be asked to take voluntary actions to prevent infection and strengthening and prioritization of the health care system will be promoted to protect those at high risk of aggravation, such as elderly people, and to ensure regular medical care.
• The national and local governments will remind the public of the need for routine infection control measures and take measures to support the public's efforts to prevent infection.

1. 1. Further promotion of vaccinations
   • 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.
2. 2. Use of tests
   • 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.
3. 3. Securing a medical care provision system
   • 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
4. 4. Response to simultaneous epidemics of novel coronavirus infection and seasonal influenza
   • 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.
5. 5. Surveillance
   • 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.
6. 6. Effective ventilation
   • 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.).
7. 7. 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.
   • 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.

<< 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 (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.

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 mucosa, aerosol inhalation, contact infection, etc.).

3. [Severity]

   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.

4. [Virus shedding period]

   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.

5. [Vaccine effect]

   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.

6. [Sublineages of the Omicron Variant]

   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.

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