国立感染症研究所

108th Meeting of the COVID-19 Advisory Board of the Ministry of Health, Labour and Welfare (November 22, 2022) Material 1

 

Evaluation of the latest infection status, etc.

Overview of the infection status

  • The number of new cases of infection nationwide (by date of report) was approximately 564 per 100,000 of the population in the last week, showing continuing increase with a ratio of this week to last week of 1.15, but with regional differences.
    It is also necessary to pay attention to the attenuation of immunity, the impact on the infection status of replacement by variant strains and, as the new year approaches, increased contact opportunities due to the reactivation of socioeconomic activities.
  • The use rate of beds is increasing nationwide, and the numbers of severe cases and deaths are also increasing.

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 Nov 29, 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 writing of this document on Nov 29.

Infection status and future outlook

Infection status
  • Nationwide, the number of new cases of infection continued to increase and the ratios to the previous week in all regions except Hokkaido are higher than 1, but the rate of increase is comparatively slow.
  • There are regional differences in the current infection status. In Hokkaido, the number of infections has surpassed the peak of the spread of infections this summer, but is now decreasing. Also in the Tohoku, Hokuriku/Koshinetsu, and Chugoku regions, the rate of increase continues to increase, and while there are many regions where the level of infection is high, the rate of increase is slowing down. In contrast, in the Tokyo metropolitan area, Kinki, Kyushu and Okinawa, the number per 100,000 of the population is lower than the national average, but the rate of increase tends to be larger than the national average. In addition, there is an increasing trend in mass infections in facilities for elderly people and medical institutions. In addition, attention should be paid to the increased number of deaths in areas where the number of infected people has increased, such as Hokkaido and Nagano.
  • The number of new cases of infection per population in each age group is higher in younger age groups, including teens. However, in some areas, the number of infected people, particularly teens, is flat or tending to decrease. In most regions, the number of new infections in elderly people is increasing, and the numbers of severe cases and deaths also continue to increase.
  • 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.Attention should also be paid to trends in the number of pediatric inpatients.
  • The incidence of seasonal influenza is lower than in the same period of usual years, but higher than in the same period of the previous two years, as an increasing trend continues in some regions.
Future outlook
  • Regarding the future infection status, the nationwide increase is expected to continue despite regional differences and uncertainty, based on the short-term forecast. It is also necessary to pay attention to the attenuation of immunity, the impact on the infection status of replacement by variants with greater immune escape ability and, as the new year approaches, increased contact opportunities due to the reactivation of socioeconomic activities.
  • Since the level of seasonal influenza shows an increasing trend in some regions, attention must be paid to future changes, including simultaneous occurrence with COVID-19.
Factors that increase and suppress infection
  1. [Immunity as a result of vaccination and infection]

    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.

  2. [Contact status]

    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.

  3. [Epidemic strains]

    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.

  4. [Climatic and seasonal factors]

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

Situation of the medical care provision system
  • Nationwide, the use of beds tended to increase, exceeding 30% in most regions, and exceeding 50% in regions with a large number of patients. The use rate of beds for severe cases is generally low, but is 20% to 30% in some regions.
  • In the field of nursing care, patients are being treated in facilities and infection is seen among elderly people and workers.
  • Cases of difficult emergency transportation continue to increase nationwide for both suspected non-COVID-19 cases and suspected COVID-19 cases.

Measures to be taken

Basic concepts
  • Measures to strengthen and focus the healthcare system should be taken in case of 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 to protect those at high risk of aggravation, such as elderly people, and to ensure regular medical care.
  • Based on the decision made by the government’s Novel Coronavirus Response Headquarters on November 18, measures to prevent the spread of infection will be taken according to the status of outpatient medical care, etc.
  • 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 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.
  2. 2. Use of tests
    • 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.
  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.

    • 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
  4. 4. Response to simultaneous epidemics of novel coronavirus infection and seasonal influenza
    • 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.
  5. 5. Surveillance and risk assessment, etc.
    • 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.
  6. 6. Effective ventilation
    • 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.
    • 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.
<< 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 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.

  4. [Virus shedding period]

    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.

  5. [Vaccine effect]

    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.

  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 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.

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

 

Copyright 1998 National Institute of Infectious Diseases, Japan

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