80th meeting of the COVID-19 advisory boardof Ministry of Health, Labour and Welfare (April 13, 2022). Material 1

Evaluation of the latest infectious status, etc.

Infection status

• The number of new cases of infection nationwide (by date of report) was approximately 274 per 100,000 in the last week, with a ratio to that for the previous week of 1.06, indicating an upward trend. The number of newly infected persons by age group has started to decrease in people in their 10s or younger, while numbers in those in their 50s and older are increasing.
• With the increasing trend in the number of new cases of infection nationwide, the number of patients being treated is still on an increasing trend. However, along with the decrease in the number of new cases of infection up to now, the numbers of severe cases and deaths are continuing to decrease.

  Effective reproduction number: On a national basis, the most recent number is greater than 1 (1.03, as of March 27), while the figure stands at 1.02 in both the Tokyo metropolitan and Kansai areas.

Local trends

* The value for new cases of infection is the number of persons per 100,000 among the total number for the latest week, based on reporting dates.

1. Hokkaido

   The number of new cases of infection is approximately 283 (approximately 351 in Sapporo City), with a ratio to that for the previous week of more than 1 (1.13). The infected individuals are mainly in their 20s or younger. Numbers in all age groups are increasing; however, those in their 40s or younger have increased particularly markedly. The use rate of beds is slightly more than 10%.

2. North Kanto

   In Ibaraki, the number of new cases of infection is approximately 299, with a ratio to that for the previous week of less than 1 (0.98). The infected individuals are mainly in their 20s or younger. The use rate of beds is approximately 20%. In Gunma, the number of new cases of infection is approximately 187, with a ratio to that for the previous week of less than 1 (0.91). In Tochigi, the number of new cases of infection is approximately 233, with a ratio to that for the previous week of more than 1 (1.02). The use rate of beds is slightly more than 20% in Tochigi and approximately 30% in Gunma.

3. Tokyo metropolitan area (Tokyo and 3 neighboring prefectures)

   In Tokyo, the number of new cases of infection is approximately 378, with a ratio to that for the previous week of more than 1 (1.01). The infected individuals are mainly in their 30s or younger. Numbers in all age groups are increasing; however, those under the age of 10, and those in their 20s and 30s have increased particularly markedly. The use rate of beds and the use rate of beds for severe cases are both slightly more than 20%. In Kanagawa, the number of new cases of infection is approximately 295, with a ratio to that for the previous week of more than 1 (1.02). In Saitama and Chiba, the numbers of new cases of infection are approximately 329 and 292, respectively, with a ratio to the previous week of less than 1 (0.98 and 0.97). The use rate of beds is slightly more than 30% in Saitama, slightly more than 20% in Chiba, and slightly less than 30% in Kanagawa.

4. Chukyo/Tokai

   In Aichi, the number of new cases of infection is approximately 244, with a ratio to that for the previous week of more than 1 (1.05). The infected individuals are mainly in their 20s or younger. Numbers in all age groups are increasing; however, those under the age of 10, and those in their 20s and 30s have increased particularly markedly. The use rate of beds is slightly more than 20%. In Gifu and Mie, the numbers of new cases of infection are approximately 215 and 241, respectively, with a ratio to that for the previous week of more than 1 (1.14 and 1.10, respectively). In Shizuoka, the number of new cases of infection is approximately 181, with a ratio to that for the previous week of less than 1 (0.93). The use rate of beds is slightly less than 30% in Gifu, slightly more than 10% in Shizuoka, and slightly more than 20% in Mie.

5. Kansai area

   In Osaka, the number of new cases of infection increased to approximately 315, with a ratio to that for the previous week of 1.12. The infected individuals are mainly in their 30s or younger. Numbers in all age groups are increasing; however, those in their 40s or younger have increased particularly markedly. The use rate of beds is slightly more than 20%, while the use rate of beds for severe cases is roughly 20%. In Hyogo, Nara, and Wakayama, the numbers of new cases of infection are approximately 241, 226, and 217, respectively, with a ratio to that for the previous week of more than 1 (1.05, 1.26, and 1.31, respectively). In Shiga and Kyoto, the numbers of new cases of infection are approximately 200 and 248, respectively, with a ratio to that for the previous week of less than 1 (0.88 and 0.99, respectively). The use rates of beds are slightly more than 20% in Shiga, Kyoto, Hyogo, and Nara, and slightly more than 30% in Wakayama. The use rate of beds for severe cases is approximately 20% in Nara.

6. Kyushu

   In Fukuoka, the number of new cases of infection is approximately 337, with a ratio to that for the previous week of more than 1 (1.11). The infected individuals are mainly in their 20s or younger. Numbers in all age groups are increasing; however, those in their 10s to 40s have increased particularly markedly. The use rate of beds is slightly more than 20%. In Saga, Nagasaki, Kumamoto, Oita, and Miyazaki, the numbers of new cases of infection are 356, 200, 257, 273, and 352, respectively, with a ratio to that for the previous week of more than 1 (1.18, 1.33, 1.21, 1.13, and 1.36, respectively). In Kagoshima, the number of new cases of infection is approximately 289, with a ratio to that for the previous week of less than 1 (0.97). The use rates of beds are slightly more than 20% in Saga and Oita, slightly less than 20% in Nagasaki, slightly less than 30% in Kumamoto, approximately 20% in Miyazaki, and slightly more than 30% in Kagoshima.

7. Okinawa

   The number of new cases of infection is the highest nationwide, at approximately 603, with a ratio to that for the previous week of more than 1 (1.22). The infected individuals are mainly in their 30s or younger. Numbers in all age groups are increasing; however, those in their 10s or younger, and those in their 30s and 40s have increased particularly markedly. The use rate of beds is slightly more than 40%.

8. Areas other than the above

   In Aomori, Iwate, Akita, Fukushima, Niigata, Yamanashi, Nagano, Okayama, Hiroshima, Kagawa, and Ehime, the numbers of new cases of infection are approximately 278, 198, 227, 225, 240, 200, 233, 222, 272, 228, and 160, respectively. The use rates of beds are slightly more than 20% in Aomori, Akita, Nagano, Okayama, and Ehime, approximately 30% in Iwate and Yamanashi, slightly more than 30% in Fukushima, slightly less than 20% in Niigata, slightly less than 30% in Hiroshima, and approximately 20% in Kagawa. The use rate of beds for severe cases is approximately 20% in Ehime.

Future outlook and measures to be taken

• Infection status

  • Regarding the number of new cases of infection nationwide, the moving average for the latest week has been increasing for more than two weeks. Looking at the data by region, although there are regions that are showing a continuous increase, some regions have leveled off. Furthermore, since the end of last year, while some regions have now decreased to levels below the peak of the spread of the infection, in other regions, the numbers have started to rise without a substantial decrease from the peak, and there are differences in changes in the infection status. Particularly in Iwate, Akita, Fukushima, Niigata, Nagano, Ehime, Oita, Miyazaki, and Kagoshima, the moving average for the latest week has exceeded the peak in the spread of the infection from the end of last year, and the ratio to that for the previous week was 1.5 in Iwate. Accordingly, attention should be paid to the spread of infection, by region. In Okinawa, which currently has the highest level of infection in Japan, the number of infections has been increasing since the end of March.

  • The number of newly infected persons by age group has shown a decreasing trend in people in their 10s or younger, while numbers in those in their 50s and older are increasing. However, the number of new cases of infection has increased in all age groups, not only in metropolitan areas such as Tokyo, Aichi, and Osaka, but also in Hokkaido, Niigata, and Okinawa. In particular, the number of infections has increased remarkably in the elderly in Okinawa, and the infection status in the elderly should also be carefully monitored in other regions.

  • While the proportion of restaurants as the place of infection is on a decreasing trend among people in their 20s, the rate of infections in workplaces is approximately 6%, showing an upward trend (roughly 3% for all ages).

  • As for the current infection status, while the pace of the spread of infection is relatively slow despite high infection levels in metropolitan areas, the infection has spread rapidly in some local cities, and attention should be paid to future trends in such areas.

• Factors that increase and suppress infection

  1. The infection situation is affected by changes in factors such as the following, which increase or suppress infection. However, an increase in contact opportunities and the replacement by the BA.2 lineage are thought to have a strong influence on the current increase in the number of infected people.

  1. [Contact patterns]

     The nighttime population is showing an increasing trend, especially in local cities. In particular, an increasing trend is being observed in most of the regions where the moving average for the latest week has exceeded the peak in the spread of the infection from the end of last year. Therefore, the effects of this trend on the future infection status should be monitored carefully. In addition, urban areas had been showing a continuous increasing trend, but turned to a decreasing trend in the latest week.

  2. [Epidemic strain]

     The replacement by the BA.2 lineage has progressed, which may be a factor in the increase in the number of newly infected individuals. In Europe, replacement by the BA.2 lineage is progressing, and the numbers of severe cases and deaths are increasing with the spread of the infection in some countries (such as the UK). Accordingly, caution is required.

  3. [Vaccinations, etc.]

     The main purpose of the third vaccination is prevention of onset and aggravation. While the third vaccination is proceeding in elderly people, the vaccination rate is still low in young people. However, it is expected that vaccination will proceed by becoming the targets for vaccination. It should be noted that the protective effect against the Omicron variant is lower than that against the Delta variant, and the duration is short. The infection prevention effect of the third vaccination is expected to diminish over time. In addition, the retention of immunity due to previous infections may affect trends in occurrence, by region.

  4. [Climate factors]

     As the temperature will rise day by day, it will become easier to ventilate, due to climate conditions. 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 spread during this period last year.

• Medical care provision system

  • The use rate of beds has been decreasing continuously with the nationwide decrease in new cases of infection, although there are some differences in the situation between regions. However, the use rate of beds has recently increased in some regions, due to an increasing trend in the number of new cases of infection (e.g., Hiroshima, Kagoshima, and Okinawa). In addition, the number of patients in home care or arranging accommodations for care is increasing in multiple regions, including Tokyo and Okinawa.

  • Regarding cases of difficult emergency transportation, the numbers of both suspected non-COVID-19 cases and suspected COVID-19 cases are decreasing, and have dropped below the peak levels of last summer. However, the number of infections has turned to an increase, in some regions.

• Efforts based on the spread of infection with the Omicron variant

  1. [Surveillance, etc.]

     It is necessary to consider effective and appropriate surveillance, in order to properly grasp trends regarding occurrences. As a system of mutant strain monitoring, genomic surveillance should be continued in order to monitor the trend regarding replacement of the BA.1 lineage with the BA.2 lineage. For severe cases, clusters, or other applicable cases, confirmation via PCR testing for mutant strains and a whole-genome analysis is required.

  2. [Efforts by local governments]

     • Local governments need to further improve the testing system in preparation for re-expansion of infection by the Omicron variant.

     • Based on the local infection status, it is necessary to continue to work to secure the required number of beds and medical staff, and to establish home-visit medical care and online medical care systems. It is still necessary to secure a system for prompt administration of oral therapeutic drugs and neutralizing antibody drugs, for patients with a risk of developing severe disease, such as elderly patients and patients with underlying diseases. It is also necessary to establish a system that allows treatment of the underlying disease to continue even if the patient has a novel coronavirus infection.

     • Prompt medical care support systems must be strengthened and thoroughly implemented at facilities for the elderly. When establishing a medical care support system, it is important for medical and nursing care departments to cooperate, and proceed in consultation with local concerned parties.

     • Based on administrative notices such as to prioritize health observation and improve efficiency in processing notices of the occurrence of patients, a system for outsourcing or centralization at the main office shall be secured, in order to efficiently carry out public health center operations and maintain the public health center functions required in the region. In addition, in the identification and home quarantine of close contacts, it is necessary in principle to take appropriate measures against infections according to the local infection status, and taking into account the characteristics of Omicron variant and the status of the spread of infection, it is necessary to focus on the cases of infection at facilities such as medical institutions and elderly facilities. At the same time, it is important to establish an environment where people can take a break from work or school if they feel even a little unwell.

     • In rural areas, the number of infected people is increasing. The above-mentioned systems need to be established in all regions.

  3. [Reinforcement of information provision to unvaccinated individuals and those receiving a third vaccination]

     • The rate of receiving a third vaccination has exceeded 80% for the elderly aged 65 years and older, and 40% overall. However, in order to minimize the number of severe and fatal cases, especially in the elderly, and to reduce patients with symptoms to the lowest possible level, it is necessary to steadily implement a third vaccination in the elderly and subjects under the age of 65, and to vaccinate as many desiring recipients as possible. From March 25, individuals from 12 to 17 years old were also subject to a third vaccination, which is being carried out as a special temporary vaccination.

     • It is important for local governments to promote the provision of information on vaccination. Along with vaccination of unvaccinated individuals, a third vaccination six months or more after the initial vaccination will restore vaccine effectiveness against the Omicron variant, as well. Accordingly, a third vaccination must also be steadily implemented. Vaccinated individuals have also been reported to have a lower risk of prolonged symptoms.

     • Vaccination of children from 5 to 11 years old is being implemented as a special temporary vaccination, and it is necessary to promote vaccination, considering that the obligation to make efforts does not apply to these children. In anticipation of preventing infections in children, it is also important for parents and the adults around them to be vaccinated.

  4. [Quarantine measures]

     It is necessary to verify the step-by-step review of quarantine measures, while taking into account the status of the current epidemic situation overseas and in Japan. In particular, attention should be paid to the recent epidemic status in the East Asian region. For individuals who are found to be positive by an entrance test, a whole-genome analysis should continue to be performed, to monitor the strains that are spreading overseas.

• Strengthening and thorough implementation of infection prevention measures based on the characteristics of the Omicron variant

  1. In situations and places where infection is widespread, it is necessary to strengthen and thoroughly implement infection control measures, based on the characteristics of the Omicron variant.

  • At schools, kindergartens, and day-care centers, in addition to thorough measures to prevent infections in children, it is necessary to recheck and thoroughly implement infection control measures, including the active promotion of vaccination of teachers, childcare workers, etc. It is important to establish an environment where children and workers can take a leave of absence, in the case of any poor health conditions. It is also necessary to consider securing educational opportunities through multiple measures, including staggered attendance and online lessons, and maintaining social functions. At the same time, thorough infection control measures are also required at home.
  • It is necessary to take thorough measures at nursing care facilities, in order to control infections in the elderly. Therefore, promotion of a third vaccination for residents and staff, as well as aggressive testing of staff is required. In addition, it is important to secure external support systems for infection control and medical care at facilities, and to promptly intervene when infection is confirmed at facilities.
  • At workplaces, it is necessary to utilize business continuity plans, and to reduce staff attendance at workplaces and opportunities for contact by adopting telework, promoting the taking of time off, and through other measures, so that social functions can be maintained. Thorough health management, the establishment of an environment where people can take a leave of absence, and the active promotion of occupational third vaccinations for workers are also needed.

• It is essential to widely share the current infection status with citizens and business operators s, and cooperate toward preventing the spread of infection.

  • The current number of new infections continues to be higher than the peak last summer. In addition, a moderate increasing trend is being observed nationwide, with a rapid spread of infection in some local cities. Therefore, it is necessary for citizens and businesses to cooperate to maintain the decreasing trend in the number of infections, call for thorough basic measures against infection, and prevent a resurgence in new cases of infection.
  • It is important for people to receive a third vaccination as soon as possible, regardless of type, once such vaccination becomes available. People with the Novel Coronavirus Disease may experience severe conditions even if they are young, and may also suffer from prolonged symptoms. Accordingly, it is necessary to promote vaccinations not only in the elderly, who have a risk of aggravation of symptoms, but also in younger persons, in order to protect their health.
  • Basic preventative measures are still effective against infection with the Omicron variant. Therefore, administrative officers, business operators, and citizens should continue to ensure the proper wearing of nonwoven masks, hand washing, ventilation, etc. The risk of infection becomes highest when the three Cs (crowded places, closed spaces, and close contact) overlap. However, even a single C should be avoided as much as possible, because the Omicron variant is highly transmissible.
  • Therefore, when going out, it is necessary to avoid situations/places with a high risk of infection, such as crowds and large gatherings, either with or without shouting/loud talking, in poorly ventilated spaces. Activities with other persons should be carried out in a small group of people who usually meet each other. Eating and drinking together should be carried out in a small group, in principle, without speaking to the extent possible, and the wearing of masks should be ensured at all times, except while eating and drinking.
  • In order to protect the lives of both ourselves and our families, and at the same time, to prevent the spread of infection with the Omicron variant, it is necessary to refrain from going out if you feel a little unwell, such as a mild fever or fatigue, and to consult with a physician and undergo tests according to local government policy.
  • In particular, caution should be exercised when meeting persons who are at a high risk of aggravation, such as the elderly.
  • Since a new fiscal year often involves the movement of people and training when joining a company or enrolling in school, and the flow of people and movement across prefectures are expected to grow as the Golden Week holidays approach, the thorough implementation of infection prevention measures is required.

<< Reference: Findings on the characteristics of the Omicron variant >>

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 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. Although limited data suggest that the incidence of pneumonia is higher than that of seasonal influenza, this needs to be investigated through various analyses. People aged 80 years and older account for a larger proportion of deaths in this wave of the spread of the infection than during last summer. Many of these people had resided at medical or elderly facilities before they were found to be infected. It has been reported that not a few persons have died from causes other than the novel coronavirus infection itself. In particular, some have refused highly invasive treatments, while others did not meet the definition of severe disease, due to a worsening of an underlying disease, or for other reasons. Attention should also be given to a possible increase in the number of infected individuals requiring hospitalization, as test-positive persons with an underlying disease may experience disease exacerbation due to infection, and elderly infected patients may develop other symptoms, such as heart failure and aspiration pneumonia, even in the absence of COVID-19 pneumonia.

4. [Duration of viral shedding]

   Viral shedding in individuals infected with the Omicron variant decreases over time. In patients with symptoms, it has been shown that the possibility of viral shedding is low at 10 days after the date of onset. In patients with no symptoms, it has been shown that viral shedding does not occur 8 days after the date of diagnosis.

5. [Vaccine effect]

   For infection with the Omicron variant, the preventive effect of a first vaccination against disease onset is 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 Omicron variant infection, as well as how these vaccine effects are attenuated after a third vaccination. Overseas, a fourth vaccination has been started in some countries. It is necessary to collect information on efficacy and safety, and to examine the need for a fourth vaccination in Japan, and the eligible persons, starting time, etc.

6. [BA.2 lineage]

   In some areas overseas, the number of cases of infection with the BA.2 lineage is increasing. In Japan, both the BA.1 lineage and the BA.1.1 lineage of the Omicron variant initially entered from overseas, after which the BA.1.1 lineage became the majority strain, and is still dominant. However, the BA.2 lineage has begun to be detected at quarantine stations and other domestic facilities, and replacement with the BA.2 lineage is progressing. Therefore, this may affect the pace of the increase (decrease) in the number of cases of infection. Analyses of the effective reproduction number, risk of domestic secondary infection, and other indices have shown that the infectivity of the BA.2 lineage is higher than that of the BA.1 lineage. The generation time in the BA.2 lineage was 15% shorter than that in the BA.1 lineage, indicating that the effective reproduction number was 26% higher. In comparing the severity of the BA.1 lineage and BA.2 lineage, some animal studies suggest that the BA.2 lineage may be more pathogenic, but it has also been reported that there is no difference in the actual risk of hospitalization or aggravation. In addition, a report from the UK indicates that there is no difference in the preventive effect of vaccination, between these two lineages. In the UK, a small number of cases of reinfection with the BA.2 lineage after infection with the BA.1 lineage have been reported, and the affected patients were reported to have mainly been unvaccinated.

7. [XE lineage]

   The XE lineage of the Omicron variant is a recombinant of the BA.1 and BA.2 lineages of the Omicron variant. The report of the WHO published at the end of March indicated that more than 600 cases have been confirmed since the first case in the UK in January. In the same report, the WHO indicated that the rate of increase in community-acquired infections was approximately 10% higher than that of the BA.2 lineage. One case of the XE lineage was identified from a sample collected on March 26 during quarantine. The National Institute of Infectious Diseases suggests that although there are no reports indicating large differences in infectivity or severity, information on the overseas infection status and findings regarding the characteristics of the virus should be collected and analyzed, as before, and genomic surveillance should be continued for purposes of monitoring.

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