82th meeting of the COVID-19 advisory boardof Ministry of Health, Labour and Welfare (April 27, 2022). Material 1

Evaluation of the latest infection status, etc.

Infection status

• The number of new cases of infection nationwide (by date of report) continued to decrease to about 226 per 100,000 in the last week, with the ratio of this week to last week at 0.91. While decreases continue mainly in metropolitan areas, there are also areas which continue to increase, such as Hokkaido and Okinawa. The number of new infections by age group continues to decrease in all age groups. While a marked decrease is seen among those in their 20s, the decrease is smaller in teens or younger.
• Along with the decrease in the number of new cases of infection nationwide, the numbers of patients receiving treatment, severe cases, and deaths continued to decrease.

  Effective reproduction number: On a national basis, the most recent number is below 1 at 0.97 (as of April 10). The figure stands at 0.94 in the Tokyo metropolitan area and 0.97 in the Kansai area.

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 353 (approximately 392 in Sapporo City), with a ratio to the previous week of more than 1 (1.12). The individuals are mainly in their 20s or younger. The number of those in their teens or younger is particularly increasing. The use rate of beds is slightly more than 10%.

2. North Kanto

   In Ibaraki, the number of new cases of infection is approximately 197, with a ratio to the previous week of less than 1 (0.81). The individuals are mainly in their 20s or younger. The number increased in teens. The use rate of beds is slightly more than 10%. In Gunma, the number of new cases of infection was approximately 169, with a ratio of this week to last week of 1.0. In Tochigi it was approximately 239, with a ratio of this week to last week of more than 1.0 (1.13). The use rate of beds is slightly less than 20% in Tochigi and slightly more than 30% in Gunma.

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

   In Tokyo, the number of new cases of infection is approximately 266, with a ratio of this week to last week of less than 1 (0.84). The individuals are mainly in their 20s or younger. It decreased in all age groups. The use rate of beds is slightly more than 20%, while the use rate of beds for severe cases is roughly 20%. In Saitama, Chiba, and Kanagawa, the numbers of new cases of infection are approximately 221, 196, and 211, respectively, with a ratio of this week to last week of less than 1 (0.87, 0.84, and 0.79, respectively). The use rates of beds are slightly more than 20% in Saitama, slightly more than 10% in Chiba, and slightly more than 20% in Kanagawa.

4. Chukyo/Tokai

   In Aichi, the number of new cases of infection is approximately 208, with a ratio of this week to last week of less than 1 (0.96). The individuals are mainly in their 20s or younger. The use rate of beds is slightly more than 20%. In Gifu, Shizuoka and Mie, the ratio of this week to last week was less than 1 (0.98, 0.90, and 0.83, respectively), with the number of new cases of infection at approximately 201, 143 and 183. The use rates of beds are slightly more than 20% in Gifu, slightly more than 10% in Shizuoka, and approximately 20% in Mie.

5. Kansai area

   In Osaka, the number of new cases of infection is approximately 239, with a ratio of this week to last week of less than 1 (0.87). The individuals are mainly in their 20s or younger. It has slightly decreased or decreased in all age groups. The use rate of beds is slightly more than 20%, and the use rate of beds for severe patients is slightly less than 20%. In Shiga, Hyogo, Nara, and Wakayama, the numbers of new cases of infection are 168, 193, 139, and 176, respectively, with a ratio of this week to last week of less than 1 (0.79, 0.80, 0.68, and 0.83). In Kyoto, the number of new cases of infection is approximately 229, with a ratio of this week to last week of 1.0. The use rates of beds are slightly more than 20% in Shiga and Hyogo, slightly less than 20% in Kyoto, slightly more than 10% in Nara, and slightly more than 30% in Wakayama.

6. Kyushu

   In Fukuoka, the number of new cases of infection is approximately 307, with a ratio of this week to last week of less than 1 (0.98). The individuals are mainly in their 20s or younger. It tends to increase in teens or younger, and decreases in other age groups. The use rate of beds is slightly less than 30%. In Saga, Kumamoto, and Miyazaki, the numbers of new cases of infection are approximately 397, 240, and 289, respectively, with a ratio to the previous week of less than 1 (0.95, 0.96, and 0.76). In Nagasaki, Oita, and Kagoshima, the numbers of new cases of infection are approximately 263, 238, and 343, respectively, with a ratio of this week to last week of more than 1 (1.17, 1.07, and 1.21). The use rates of beds are approximately 30% in Saga, slightly more than 20% in Nagasaki, Oita, and Miyazaki, slightly less than 30% in Kumamoto, and approximately 40% in Kagoshima.

7. Okinawa

   The number of new cases of infection is the highest nationwide, at approximately 644, with a ratio of this week to last week of 1.0. The infected individuals are mainly in their 30s or younger. In particular, the increase among those in their teens or younger is marked. On the other hand, it decreased in those in their 80s and older. The use rate of beds is slightly less than 50%.

8. Areas other than the above

   In Aomori, Iwate, Miyagi, Akita, Fukushima, Niigata, Ishikawa, Yamanashi, Nagano, Okayama, Hiroshima, Yamaguchi, Kagawa, and Ehime, the numbers of new cases of infection are approximately 215, 195, 171, 191, 213, 158, 193, 130, 190, 221, 235, 108, 242, and 142, respectively. The use rates of beds are slightly more than 20% in Aomori, Iwate, Miyagi, Akita, Ishikawa, Nagano, Okayama, Yamaguchi, and Kagawa, slightly more than 30% in Fukushima and Yamanashi, approximately 20% in Niigata, approximately 30% in Hiroshima, and slightly less than 20% in Ehime.

Future outlook and measures to be taken

• Infection status

  • Nationwide, the number of new cases of infection continues to decrease, especially in metropolitan areas, while in Hokkaido and Okinawa it continues to increase, and there are differences in the transition of infection status. By region, in Iwate, Akita, Fukushima, Shimane, Miyazaki and Kagoshima, the moving average for the latest week has exceeded the peak since the end of last year. Accordingly, attention should be paid to the spread of infection, by region.

  • The number of new infections by age group tends to decrease in all age groups, but the decrease is smaller and the number of new infections per population is highest in teens or younger. In the Tokyo metropolitan area, the number of newly infections continues to decrease in almost all age groups, while in Hokkaido and Okinawa, the number of newly infections continues to increase among teens or younger. In Okinawa, decreases were seen among people in their 80s and older, but numbers leveled off in people in their 60s and 70s. The infection status in the elderly should continue to be carefully monitored in other regions.

  • The proportion of schools as the place of infection continues to increase.

  • In the current infection status, the number of new cases of infections continues to decrease nationwide, mainly in metropolitan areas, but the number of new infections continues to increase in some areas, such as Hokkaido and Okinawa. Considering that the situation in all regions is still higher than the peak of last summer, and that there are many regions with repeated increases and decreases, it is necessary to continue to pay close attention to future trends.

• 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, the increase in contact opportunities and replacement by the BA.2 lineage are thought to have a strong influence on the recent increase in the number of infected people. In addition, the decreasing trend now seen may be affected by the acquisition of immunity by vaccination, and by the efforts of citizens to avoid places and situations where the risk of infection is high.

  1. [Contact patterns]

     The nighttime population is showing an increasing trend in more than half the country. Depending on the time of day, there are areas that are near the peak of the nighttime population at the end of last year, and areas that exceed the peak. In addition, movement and contact may increase toward Golden Week, and it is necessary to pay attention to the impact on the infection status.

  2. [Epidemic strain]

     It is estimated that replacement by the BA.2 lineage has progressed to about 90% nationwide, which may be a factor in the increase in the number of newly infected individuals. Overseas, replacement by the BA.2 lineage is progressing, and the number of deaths is 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 the elderly and also in young people, it is expected that the vaccination rate will further improve as young people become targets of 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

  • In Okinawa, the number of inpatients and the use rate of beds remain high. In addition, there are other areas where the use rate of beds exceeds 30%, and the number of home care recipients and medical treatment adjustments continues to increase.

  • Cases of difficult emergency transportation dropped below the peak levels of last summer, and the numbers of both suspected non-COVID-19 cases and suspected COVID-19 cases continue to decrease. However, the number increased 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 also need to inspect the medical care/testing system and the public health center system in order to strengthen the response based on the characteristics of the Omicron variant.
     • In deaths that occurred at home after January this year, approximately 80% of the patients have been aged 70 years and older, similarly to the trend of all deaths during the same period, suggesting that many patients die from factors other than the novel coronavirus. The vaccination rate in these fatal cases was confirmed to be a certain number of those who had completed the second vaccination, due to the progress of vaccination in Japan. Local governments are trying to speed up contact with infected people who are at high risk of becoming severely ill, and it is important to continue to make efforts to provide the necessary medical care to home care recipients.
     • 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 some rural areas, the number of infected people is now 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]
     • As of April 26, the rate of third vaccinations was about 87% for the elderly aged 65 years and older, and about 51% overall. Vaccination of elderly people is expected to reduce the risk of severe illness and death. In order to minimize the number of severe and fatal cases, and to reduce patients with symptoms to the lowest possible level, it is necessary to steadily implement a third vaccination to the subjects, and to vaccinate as many desiring recipients as possible.
     • 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. Therefore, 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, and cooperate toward preventing the spread of infection.

  1. The current number of new infections continues to be higher than the peak last summer. In addition, as Golden Week approaches, it will be the season when there are more opportunities for leisure activities such as travel, events, shopping, and going out. Previously, increased contact with people who are not usually met, such as at annual events, has triggered the spread of infection. 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 daily health management, to prevent a resurgence in new cases of infection. It is also necessary to keep in mind health management when going to school or commuting after Golden Week.

  2. [Vaccination]

     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.

  3. [Thorough infection control]

     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.

  4. [When going out or traveling]

     Crowded or poorly ventilated places with a large number of people and loud voices, where the risk of infection is high, should be avoided. 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 done in a small group without speaking to the extent possible, and masks should be worn at all times except while eating and drinking. Basic infection control measures should be thoroughly implemented in transit, avoiding activities with a high infection risk at the destination, and a third vaccination or a test should be received in advance when traveling or going home.

  5. [Health management]

     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 severe illness, such as the elderly.

<< 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]

   Infection by the BA.2 lineage is spreading overseas. In Japan, the influx of the Omicron variant from overseas was initially both BA.1 and BA.1.1, but then BA.1.1 came to dominate. Currently, 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. More than 1,500 cases have been confirmed since the first case in the UK in January. The WHO report 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)