国立感染症研究所

92nd Meeting of the COVID-19 Advisory Board of the Ministry of Health, Labour and Welfare (July 27, 2022). Material 1

Evaluation of the latest infection status, etc.

Infection status

• Nationwide, the number of new cases of infection (by date of report) was about 978 per 100,000 in the last week, continuing to rapidly increase at a ratio of this week to last week of 1.89 (although the effect of 3 consecutive holidays must be considered when comparing to the previous week).
  It is again the highest level of infection ever in Japan, increasing in all age groups.
• As the number of new cases of infection increases, the number of patients receiving medical treatment continues to increase, and although the use rate of beds shows regional differences, and in some regions, there is a heavy burden on the medical care provision system.
  In addition, the numbers of severe cases and deaths continue to increase, and attention should be paid to future trends.

  Effective reproduction number: On a national basis, the most recent number is greater than 1 (1.24, as of July 10), while the figure stands at 1.26 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 was approximately 494 (about 569 in Sapporo City), with a ratio to the previous week of 2.29. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly less than 20%.

2. North Kanto

   In Ibaraki, Tochigi, and Gunma, the numbers of new cases of infection were about 530, 682, and 692, with ratios to the previous week of 2.08, 2.57, and 2.10, respectively. In Ibaraki, Tochigi, and Gunma, they were mainly in their 30s or younger. The use rates of beds are slightly less than 50% in Ibaraki, approximately 40% in Tochigi, and approximately 50% in Gunma.

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

   The number of new cases of infection in Tokyo was approximately 1,438, with a ratio to the previous week of 1.79. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly more than 40%, while the use rate of beds for severe cases is slightly more than 50%. In Saitama, Chiba, and Kanagawa, the numbers of new cases of infection were about 927, 892, and 875, with ratios to the previous week of 1.78, 1.85, and 1.50, respectively. The use rates of beds are approximately 50% in Saitama, slightly more than 50% in Chiba and slightly less than 70% in Kanagawa.

4. Chukyo/Tokai

   The number of new cases of infection in Aichi was approximately 1,130, with a ratio to the previous week of 2.17. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly less than 40%. In Gifu, Shizuoka, and Mie, the numbers of new cases of infection were about 758, 885, and 730, with ratios to the previous week of 2.16, 2.19, and 1.83, respectively. The use rates of beds are slightly more than 30% in Gifu, approximately 70% in Shizuoka, and slightly more than 40% in Mie.

5. Kansai area

   The number of new cases of infection in Osaka was approximately 1,555, with a ratio to the previous week of 2.18. The infected individuals are mainly in their 30s or younger. The use rate of beds is approximately 50%, while the use rate of beds for severe cases is slightly less than 30%. In Shiga, Kyoto, Hyogo, Nara, and Wakayama, the numbers of new cases of infection were about 717, 1,035, 1,060, 826, and 771, with ratios to the previous week of 1.57, 1.92, 1.91, 1.49, and 1.73, respectively. The use rates of beds are slightly more than 50% in Shiga and Hyogo, slightly more than 30% in Kyoto, slightly more than 40% in Nara, and slightly more than 60% in Wakayama.

6. Kyushu

   The number of new cases of infection in Fukuoka was approximately 1,481, with a ratio to the previous week of 2.01. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly more than 60%. In Saga, Nagasaki, Kumamoto, Oita, Miyazaki, and Kagoshima, the numbers of new cases of infection were about 1,231, 834, 1,461, 1,055, 1,097, and 1,133, with ratios to the previous week of 1.58, 2.01, 1.63, 1.73, 1.78, and 1.70, respectively. The use rates of beds are slightly more than 40% in Saga, slightly more than 50% in Nagasaki, approximately 60% in Kumamoto, slightly more than 40% in Oita, slightly less than 40% in Miyazaki, and slightly more than 60% in Kagoshima.

7. Okinawa

   The number of new cases of infection was the highest nationwide at approximately 2,260, with a ratio of this week to last week of 1.46. The infected individuals are mainly in their 30s or younger. The use rate of beds is slightly more than 80%, while the use rate of beds for severe cases is slightly more than 30%.

8. Areas other than the above

   Miyagi, Akita, Tochigi, Niigata, Toyama, Yamanashi, Shimane, and Kagawa had ratios to the previous week of 2.85, 2.67, 2.57, 2.35, 2.61, 2.38, 1.18, and 2.11, respectively. The number of new cases of infection was approximately 969 in Shimane. The use rates of beds are approximately 60% in Aomori, approximately 50% in Fukushima and Hiroshima, and slightly more than 50% in Ishikawa.

Future outlook and measures to be taken

• Infection status

  • The number of new cases has again hit a record high nationwide, and all prefectures have greatly exceeded the previous spread of infection as the rapid spread of infection continues. The infection level in Okinawa continues to be higher than in other regions, and the highest so far, while the use rate of beds is also severe. In addition, the rapid increase in cases of infection and close contact are having an impact on social activities overall.

  • The number of new cases of infection by age group is increasing nationwide in all age groups, including the elderly. In the past, increase in the number of severe cases and deaths has tended to lag behind a rapid increase in the number of new infections, and there are concerns about these increases as the number of infected elderly people increases.

  • Regarding the future infection situation, the epi curve of the onset date and short-term forecasts in large cities predict that the number of new infections will continue to increase or at best level off in many regions and will reach record highs nationwide. Close attention should be paid to the medical care provision system, with the utmost caution.

  • Factors in the continued increase in the number of infected individuals include (1) the gradual diminishing of the immunity acquired by the third vaccination and infection, (2) the increased contact that is expected due to the influence of summer vacation etc., and (3) the presumed replacement of the Omicron variant by lineages such as BA.5.

  • Regarding the places of infection of new cases, there is an increasing trend at home and a decreasing trend at schools (it must be kept in mind active epidemiological surveillance is focused on large cities, and that infection routes are not fully understood).

• 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. [Vaccination]

     It has become clear that as a certain period elapses after the third vaccination, the infection prevention effect is attenuated compared to the aggravation prevention effect. In addition, the immunity acquired from previous infections is expected to similarly decline in the future.

  2. [Contact patterns]

     The nighttime population is decreasing in many regions, including large cities such as Tokyo, Aichi, and Osaka. However, in some areas the number of infections has leveled off or turned to increase.

  3. [Epidemic strain]

     After the prevalence of BA.2 lineage, it is estimated that the BA.5 lineage will become mainstream and replace it. In particular, the BA.5 lineage is thought to increase the number of infected persons more easily, and there is concern about immune escape, which may be a factor in increasing the number of infected persons.

  4. [Climatic factors]

     It is a time when indoor activities increase due to rising temperatures, but ventilation may be difficult because air conditioning is prioritized.

• Medical care provision system

  • Nationwide, the burden on the outpatient examination system is increasing, and although there are regional differences in the use rate of beds, it has risen to 30% in most regions, including large cities, due to the increase in the number of new infections, and the number of regions exceeding 50% is also increasing. In addition, the numbers of home care recipients and medical treatment adjustments are increasing in most regions and are rapidly increasing in some regions.

  • Especially in Okinawa, the use rate of beds continues to rise, exceeding 80%, and the situation is severe, and nationwide, the increasing number of infections among healthcare workers is placing a burden on the medical care provision system. In the field of nursing care also, the difficult situation continues due to the increasing numbers of patients being treated in facilities and of infections among workers.

  • The positive rate of the test has increased, and there is concern whether the test is being appropriately received by those who need it, such as people with symptoms.

  • Cases of difficult emergency transportation continue to increase rapidly nationwide for both suspected non-COVID-19 cases and suspected COVID-19 cases, although there are regional differences. In addition, careful attention should be paid to the increase in ambulance transportation due to heat stroke.

• Measures and basic concepts

  • In the midst of rapid spread of infection, it is necessary to reduce as much as possible the chances of contacts which risk infection, based on the various knowledge that Japanese society has already learned. Also, in order to maintain socio-economic activities, it is necessary to work on methods for people to avoid infecting and being infected.

  • To this end, 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. It is also necessary to make further efforts to strengthen the medical care provision system.

  1. 1. Further promotion of vaccination
     • Since the 4th vaccination has a limited effect in preventing infection, it has been promoted at facilities for the elderly with the aim of preventing aggravation. However, in light of the recent rapid spread of infection, the target has been expanded to include healthcare workers and those working in facilities for the elderly.
     • It is necessary to continue to promote the third vaccination for the age groups and regions in which the vaccination rate is low.
  2. 2. Use of tests

     1. Based on the recommendations of the 17th meeting of the Novel Coronavirus Subcommittee, the national and local governments are required to secure a system that enables testing, and further utilize testing.

     2. [The Elderly]
        • Frequent tests (about 2 or 3 times a week for facility workers) are required for workers at facilities for the elderly.
        • Depending on the circumstances in the area, testing at appropriate occasions (e.g. Obon, when contact with relatives who have returned home is expected) is recommended for users of facilities for the elderly.
     3. [Children]
        • Depending on the circumstances in the area, if a cluster occurs it is necessary to carry out frequent testing of teachers and staff at nursery schools and kindergartens.
        • At the discretion of local governments and schools, it is necessary to thoroughly observe health, test those with some symptoms, and prevent outbreaks while allowing participation in club activities such as tournaments and school trips.
     4. [Young people]
        • Preliminary testing is further recommended when having a meal with a large number of people or when interacting with the elderly (especially when contacting them during the Obon/summer vacation homecoming).
        • It is necessary to establish a system for symptomatic patients to test themselves with a qualitative antigen test kit before visiting a medical institution. A stable supply, including distribution, is important so that those who need them can secure antigen qualitative test kits.
  3. 3. Effective ventilation
     • Based on the recommendations of the 17th meeting of the Novel Coronavirus Subcommittee, it is necessary to publicize and recommend effective ventilation methods in the summer when ventilation becomes insufficient due to the use of air conditioners (how to create airflow considering aerosols, installation of partitions that do not block airflow, etc.).
  4. 4. Securing a medical care provision system
     • Prefectural governments need to inspect and strengthen the following systems with the support of the national government, in preparation for further spread of infection.
     • Establishing and utilizing a call center, strengthening a system that enables prompt and smooth testing and safe home care
     • Building and strengthening a system that enables appropriate and early administration of therapeutic drugs.
     • Systematic preparation for further securing of hospital beds.
     • Promotion of flexible and efficient use of hospital beds through zoning for each hospital room.
     • Response to the increasing trend of ambulance transport difficulties. In addition to confirming the acceptance system for patients other than COVID-19 patients, spreading awareness of heat stroke prevention and warning of increased emergency transportation due to heat stroke. In addition, those who are at being treated home or staying overnight should be encouraged to use the consultation service. Furthermore, those who wish to visit a medical facility should be informed of the symptoms required for requesting an ambulance.
     • Further strengthen medical support for testing and facilities for the elderly, based on an intensive implementation plan at facilities for the elderly.
     • Further promote the reduction of burdens, such as hospitalization coordination and outsourcing/unification of operations by the hospitalization coordination division, so that public health center operations will not be strained.
  5. 5. Re-inspection and implementation of basic infection control
     • Continue proper wearing of nonwoven masks, hand hygiene, ventilation, etc. Avoid situations with a high risk of infection, such as the three Cs, congestion, or loud voices. Eating and drinking should be done with as few people as possible, and masks should be worn except while eating and drinking. People with symptoms such as sore throat, cough, and fever should refrain from going out. In order to reduce the chances of contact, it is necessary to re-inspect and thoroughly enforce basic infection countermeasures, such as promoting the use of telework again at the workplace. In addition, organizers of events, meetings, and such should fully evaluate the epidemic situation and risk of infection in the area, and consider whether or not to hold the meeting, and if it is held, measures should be taken to minimize the infection risk.

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

3. [Severity]

   It has been suggested that infection with the Omicron variant presents a lower risk of hospitalization or aggravation than the Delta variant. However, analyses to date show that the fatality due to infection with the Omicron variant is higher than that due to seasonal influenza. It is also suggested that the incidence of pneumonia is higher than that of seasonal influenza, but given the limited data, it needs to be investigated by various analyses. The death toll from the previous outbreak compared to last summer's outbreak had a higher proportion of people aged 80 and over. It is reported that there are many cases in which the new coronavirus infection is not the direct cause of death, for example, people who have been in a facility for the elderly before the infection are infected and die due to the worsening of the underlying disease. Attention should also be paid to worsening of the condition of elderly infected people and infected people with an underlying disease, and to the onset of heart failure and aspiration 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 from 10 days after the date of onset. In patients with no symptoms, it has been shown that viral shedding does not occur from 8 days after the date of diagnosis.

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, as well as information regarding how these vaccine effects are attenuated after a third vaccination. Regarding the fourth vaccination, while the preventive effect against aggravation was not reduced for 6 weeks, the preventive effect against infection was limited, and it was reported that the effect lasted only for a short time.

6. [Omicron variant sublineages]

   Worldwide, the proportion of the BA.5 lineage is increasing, suggesting that this lineage is superior to the BA.2 lineage in terms of increasing the number of infected people. The number of positive tests is on the rise globally, as replacement by the BA.5 lineage proceeds. The BA.5 lineage has shown a tendency to escape existing immunity compared with the BA.1 and BA.2 lineages, but no clear findings on the infectivity have been shown. The effective reproduction number of the BA.5 lineage calculated based on the data of Tokyo was about 1.27 times that of BA.2. It was also estimated that it was about 1.3 times higher in samples collected from private testing institutions nationwide.

   According to the WHO report, the findings accumulated from multiple countries indicate that there is no increase in the severity of the BA.5 lineage compared to existing Omicron variants. On the other hand, the pathogenicity of the BA.5 lineage is reportedly higher than that of the BA.1 and BA.2 lineages, based on Japanese laboratory data, but it has not been confirmed clinically at this time. Although it is unknown whether it is due to the traits of the BA.5 lineage, it should be noted that the numbers of inpatient cases and severe cases are increasing in countries where the number of infected people is increasing mainly in the BA.5 lineage.

   The BA.5 lineage has been detected both in Japan and in quarantine. According to genomic surveillance, the detection rate of the BA.5 lineage is increasing, and replacement has presumably progressed. It is necessary to continue to collect and analyze the situation and findings in other countries regarding the characteristics of the virus, and to continue monitoring by genome surveillance.

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