85th meeting of the COVID-19 advisory boardof Ministry of Health, Labour and Welfare (May 25, 2022). Material 1

Evaluation of the latest infection status, etc.

Infection status

• The number of new cases of infection nationwide (by date of report) was about 188 per 100,000 in the last week, decreasing to a ratio of this week to last week of 0.91.
• The number of new cases of infection by age group continued to increase for persons younger than 10, but slightly decreased or decreased in other age groups.
• With the number of new cases of infection starting to decrease nationwide, the number of patients being treated also tends to decrease.
  On the other hand, the number of severe cases continues to decrease, and the number of deaths has leveled off.

  Effective reproduction number: On a national basis, the most recent number is above 1 (1.04 as of May 8), while the figure stands at 1.02 in the Tokyo metropolitan area and 1.06 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 291 (roughly 309 in Sapporo City), with a ratio of numbers for this week to last week of less than 1 (0.81). The individuals are mainly in their 20s or younger. The number is increasing only in those younger than 10, and is slightly decreasing or decreasing in other age groups. The use rate of beds is approximately 20%.

2. North Kanto

   In Ibaraki, the number of new cases of infection is approximately 123, with a ratio of numbers for this week to last week of less than 1 (0.89). The individuals are mainly in their 20s or younger. It increased or slightly increased in those younger than 10 and those aged 70 or older, while it slightly decreased or decreased for other age groups. The use rate of beds is approximately 10%. In Tochigi and Gunma, the numbers of new cases of infection are approximately 124 and 120, respectively, with a ratio of numbers for this week to last week of less than 1 (0.88 and 0.93). The use rates of beds are slightly more than 10% in Tochigi and slightly less than 20% in Gunma.

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

   In Tokyo, the number of new cases of infection is approximately 172, with a ratio of this week to last week of less than 1 (0.92). The individuals are mainly in their 20s or younger. It increased or slightly increased in those younger than 10 and those aged 80 or older, while it slightly decreased or decreased for other age groups. The use rate of beds and the use rate of beds for severe cases are both slightly more than 10%. In Saitama, Chiba, and Kanagawa, the numbers of new cases of infection are approximately 116, 105, and 135, respectively, with a ratio of this week to last week of less than 1 (0.82, 0.90, and 0.91). The use rates of beds are slightly less than 20% in Saitama, approximately 10% in Chiba and slightly more than 10% in Kanagawa.

4. Chukyo/Tokai

   In Aichi, the number of new cases of infection is approximately 195, with a ratio of this week to last week of less than 1 (0.95). The individuals are mainly in their 20s or younger. It increases in patients younger than 10 and slightly increases in patients in their 30s and 60s. The number is slightly decreasing or decreasing in other age groups. The use rate of beds is slightly less than 20%. In Gifu, Shizuoka and Mie, the ratio of this week to last week was less than 1 (0.99, 0.93, and 0.98, respectively), with the number of new cases of infection at approximately 198, 176 and 157. The use rates of beds are 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 is approximately 219, with a ratio of this week to last week of less than 1 (0.92). The individuals are mainly in their 20s or younger. The number is increasing only in those younger than 10, and is slightly decreasing or decreasing in other age groups. The use rate of beds is slightly more than 20%, while the use rate of beds for severe patients is slightly more than 10%. In Kyoto, Hyogo, Nara, and Wakayama, the numbers of new cases of infection are approximately 228, 180, 136, and 166, respectively, with a ratio of this week to last week of less than 1 (0.99, 0.91, 0.83, and 0.85). In Shiga, the number of new cases of infection is approximately 179, with a ratio of this week to last week of more than 1 (1.02). The use rates of beds are slightly less than 20% in Shiga and Hyogo, slightly more than 10% in Kyoto and Nara, and slightly less the 30% in Wakayama.

6. Kyushu

   In Fukuoka, the number of new cases of infection is approximately 259, with a ratio of this week to last week of less than 1 (0.95). The individuals are mainly in their 20s or younger. It increased or slightly increased in those younger than 10 and those aged 80 or older, while it slightly decreased or decreased for other age groups. The use rate of beds is slightly more than 20%. In Saga, Nagasaki, Oita, Miyazaki, and Kagoshima, the numbers of new cases of infection are approximately 209, 215, 223, 298, and 276, respectively, with a ratio of this week to last week of less than 1 (0.87, 0.97, 0.97, 0.88, and 0.96). In Kumamoto, the number of new cases of infection is approximately 243, with a ratio of this week to last week of more than 1 (1.03). The use rates of beds are slightly more than 10% in Saga, slightly more than 20% in Nagasaki and Miyazaki, approximately 30% in Kumamoto and Kagoshima, and approximately 20% in Oita.

7. Okinawa

   The number of new cases of infection is the highest nationwide, at approximately 931, with a ratio of this week to last week of less than 1 (0.91). The infected individuals are mainly in their 30s or younger. It increased in those younger than 10 and those aged 70 or older, while it slightly decreased or decreased for other age groups. The use rate of beds is slightly less than 50%, while the use rate of beds for severe cases is slightly more than 20%.

8. Areas other than the above

   In Aomori, Iwate, Akita, Yamagata, Fukushima, Ishikawa, Tottori, Hiroshima, Yamaguchi, Kagawa, and Kochi, the numbers of new cases of infection are approximately 180, 129, 106, 118, 151, 289, 132, 280, 159, 235, and 226, respectively. The use rates of beds are slightly more than 20% in Aomori, Akita, Ishikawa, Yamaguchi, and Kagawa, slightly less than 30% in Iwate, Fukushima, and Hiroshima, and about 20% in Yamagata, Tottori, and Kochi.

Future outlook and measures to be taken

• Infection status

  • The number of new cases of infection did not continue to increase after the latter half of Golden Week, and it continues to decrease nationwide except for some regions. However, since there is a concern that the number of patients with infection may increase again from the epi curve on the date of onset, it is necessary to pay attention to future trends. By region, the moving average for last week is lower than the peak of last summer in the Tokyo metropolitan and other areas. In contrast, the moving average for last week is higher than the peak from the end of last year in Okinawa and Miyazaki. In particular, the number of new cases of infection in Okinawa continues to be the highest nationwide, although there is a decreasing trend. In other regions as well, it will be necessary to continue to pay attention to changes in the number of infected people.

  • The number of new cases of infection by age group continued to increase for persons younger than 10, but slightly decreased or decreased in other age groups. There is a marked increase in many regions, particularly in those under the age of 10, who continue to increase. Furthermore, in Okinawa, the increase in those under the age of 10 is particularly remarkable. The number aged 70 years or older also increases, and therefore it is necessary to continue watching the status of infection in the elderly.

  • Regarding the place of infection of newly infected people, the proportion in schools, nursery schools, kindergartens, etc. is high, while the proportion in restaurants is decreasing.

  • As for the future infection situation, it may be affected by factors that increase infections, such as the ongoing substantial replacement by the BA.2 lineage, as well as factors that suppress infection, such as a third vaccination, etc.

• Factors that increase and suppress infection

  1. It is thought that infection status is affected by the following changes in factors that increase and suppress infection .

  1. [Contact patterns]

     The nighttime population is showing an increasing trend in more than half the regions in the country. In some areas the number increases as much as the peak at the end of last year, and it is necessary to pay attention to the impact on the infection status.

  2. [Epidemic strain]

     The replacement by the BA.2 lineage has generally progressed, and compared to the time when the BA.1 lineage was dominant, it may be a factor in the increase in the number of newly infected individuals and the slowdown in the decrease.

  3. [Vaccinations, etc.]

     The main purpose of a 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. However, it should be noted that as a certain period elapses after the third vaccination, the preventive effect against infection is expected to diminish from those who received vaccination earlier. In addition, the retention of immunity due to previous infections may affect trends in occurrence, by region.

  4. [Climate factors]

     When the temperature rises, it becomes easier to ventilate, due to climate conditions. However, when the temperature rises or the rainy season begins, rainfall may increase indoor activities.

• Medical care provision system

  • In Okinawa, the number of inpatients and the use rate of beds are on a decreasing trend, but the use rate of beds for severe cases remains at the 20% level. Nationwide, with a continuing decreasing trend in the number of new cases, the use rate of beds is decreasing in nearly half the regions.

  • Cases of difficult emergency transportation, both suspected non-COVID-19 cases and suspected COVID-19 cases, tended to decrease, but there are some regions where the number is increasing regardless of the increase or decrease in the number of infected people, showing regional differences.

• 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. In addition, it is necessary to continue monitoring the trends of variants through genomic surveillance. For severe cases, clusters, and 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.
     • It is necessary to continue efforts to establish the required system for providing medical care based on the regional infection status.
     • When strengthening and thoroughly implementing a medical care support system for the elderly, 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, in order to efficiently carry out public health center operations and maintain the public health center functions required in the region, it is important to secure a system for outsourcing or centralization at the main office.
  3. [Reinforcement of information provision to unvaccinated individuals and those receiving a third vaccination, etc.]
     • As of May 24, the rate of third vaccinations was about 89% for the elderly aged 65 years and older, and about 58% overall. It is necessary to steadily implement a third vaccination in subjects, and to vaccinate as many desiring recipients as possible. A fourth vaccination will be implemented from May 25 as a special temporary vaccination to prevent aggravation in persons aged 60 years or older, persons with underlying diseases at high risk of severe symptoms, and other persons deemed by doctors to be at a high risk of severe symptoms.
     • It is important for local governments to promote the provision of information on vaccination. The third and fourth vaccinations must also be steadily implemented, along with vaccinations for unvaccinated persons. 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 addition, while continuing pre-departure tests and responding to the risk of inflow, whole genome analysis should be continued for those who are positive in the immigration test to monitor strains circulating 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.

  • In schools, kindergartens, nursery schools, etc., infection control measures including active promotion of vaccinations for teachers and nursery teachers will be thoroughly implemented, as well as infection control measures for children, while sharing situations where the risk of infection in children and students increases with staff, children, parents, etc. It is also necessary to continue educational activities and social functions as far as possible. 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. 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, workers need to be actively examined. It is also necessary to proceed with the fourth vaccination of residents to prevent aggravation. 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.
  • In the workplace, in order to maintain social functions, in addition to utilizing business continuity plans, efforts are required to reduce the number of employees attending work by utilizing telework and promoting the taking of time off, and to reduce contact opportunities. And, thorough health management of employees and securing an environment where they can take a leave of absence if they are even a little unwell are necessary. In addition, a third vaccination in the workplace should be actively promoted.

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

  1. Nationwide, the situation is still higher than the peak last summer, and there is also concern about the possibility of rebound because the factors that increase and suppress infection will continue. For this reason, it is necessary for citizens and businesses to cooperate to maintain the decreasing trend in the number of infections, and to call for thorough basic measures against infection and daily health management, in order to prevent a resurgence in the number of new cases of infection.

  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.

     On the other hand, it is not always necessary to wear a mask as before if it is possible to secure sufficient distance from surrounding people outdoors, or even when it is not possible to get sufficient distance from the surrounding people outdoors if there is little (or almost no) conversation. However, it is still necessary to wear them outdoors in a crowd. After clarifying that not all preschoolers are required to wear masks, and that they shall not be forced to wear them, the information should be disseminated widely and thoroughly.

  4. [When going out]

     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.

  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 infection by the Omicron variant, as well as information regarding how these vaccine effects are attenuated after a third vaccination.

6. [BA.2 lineage]

   Overseas, the number of infected patients has increased, while replacement with the BA.2 lineage is progressing. However, the number is currently decreasing worldwide. In Japan, the influx of the Omicron variant from overseas initially comprised both BA.1 and BA.1.1; however, BA.1.1 has since become dominant. Currently, it has been largely replaced by the BA.2 lineage. 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, BA.4, BA.5, and BA.2.12.1 lineages]

   The XE lineage of the Omicron variant is a recombinant of the BA.1 and BA.2 lineages of the Omicron variant. Two cases of the XE lineage were identified in quarantine. The WHO report indicated that the rate of increase in community-acquired infections was approximately 10% higher than that of the BA.2 lineage. The BA.4, BA.5, and BA.2.12 1 lineages have been detected in quarantine. Of these, the BA.5 and BA.2.12.1 lineages have also been detected in Japan. In some countries and regions, the detection rates of the BA.4, BA.5, and BA.2.12.1 lineages have increased, and the BA.2 lineage has been replaced by these variants, suggesting its superiority in terms of an increase in the number of infected patients. The National Institute of Infectious Diseases has suggested 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)