The "6th wave", in which the Omicron strain of the new coronavirus expanded, has exceeded its peak, and the priority measures such as the prevention of spread that have been applied to various places have been lifted for the first time in two months.
However, the rate of decrease in infections is gradual, and the number of infected people continues to be high, more than double the peak when the state of emergency was declared last summer.
Some people are worried that the infection may not go down and lead to the next "7th wave".
Why can't the infection go down?
(Yuta Mizuno, Ima Mitani, Reporter, Science and Culture Department, Yukiaki Matsuo, Reporter, Social Affairs Department)
“6th wave” Infection reduction speed is gradual
In the sixth wave, when the infection spread rapidly earlier this year, the number of newly infected people nationwide peaked at about 105,600 on February 5.
On average for one week, the number of people exceeded 93,000 around February 10, and then it started to decrease. However, as of March 17, about a month later, the number was about 51,000, a decrease of about 45%. And, it has not reached half.
The peak of the fifth wave last summer was 25,992 on August 20, with a daily average of 25,992, and a weekly average of around 23,000 on August 25.
On September 29, just over a month later, the average weekly number was about 2190, a decrease of about 90%.
In the 5th wave, the infection dropped sharply to a low level, but in the 6th wave, the rate of decrease was slow.
At a press conference after the expert meeting of the Ministry of Health, Labor and Welfare held on March 15, Chairman Takaji Wakita said, "Although it is declining nationwide, the rate of decrease is still slow and the rate of decrease is steadily increasing. The situation is quite different from the convergence phase of the 5th wave in 2021. From now on, human contact will increase due to consecutive holidays, spring holidays, yearly changes, etc., and the more infectious "BA.2" strain virus There is a possibility that the number of infected people will start to increase again due to the progress of replacement, so we need to be careful. "
Reason for slow decrease
Experts cite the reason why the rate of decline is
gradual
. He
points out that what is going on is big.
Delayed third vaccination spread to the elderly
In the fifth wave, more than 70% of elderly people aged 65 and over completed two doses in late July 2021, when the infection spread rapidly, and the infection spread among the younger generation is older. It is analyzed that a rapid decrease was seen because there were few transitions to the elderly.
On the other hand, at the stage of the 6th wave in early January 2022, the effect of preventing infection had decreased after the second inoculation, and 1 of the elderly people aged 65 and over who received the third inoculation. It was less than%.
The inoculation rate remained at about 15% even on February 5, when the number of infected people was the highest, and it seems that the infection spread to the elderly after the spread of the infection in the younger generation.
Infection of the elderly continues, and according to the Ministry of Health, Labor and Welfare, the number of clusters confirmed at welfare facilities for the elderly nationwide continues to be as high as 341 even in the week leading up to the 14th of this month.
(Professor Satoshi Kutsuna, Osaka University, who specializes in infection control)
"In Osaka Prefecture, the sickness of the bed has continued for a considerable period of time, and even if an infected person appears in a facility for the elderly, he cannot be hospitalized and must continue care at the facility. There is a situation, and the situation is still close to that. The infected people stay in the facility, so the infection spreads around. The elderly people cannot be hospitalized due to the tight medical treatment, and the number of infected people increases in the facility, which is a vicious cycle. Now, about half of the clusters that occur in Osaka Prefecture are related to the elderly, and it is one of the factors that the infection does not decrease as expected. "
(Participating in an expert meeting of the Ministry of Health, Labor and Welfare) Dr. Yoshihiro Takayama, Okinawa Prefectural Chubu Hospital)
"In Okinawa, the number of infected people started to increase after the number of infected people had bottomed out, but by the beginning of March, the number of elderly people had already increased. More than 60% have completed booster vaccinations, and infections among the elderly continue to decline. In Japan, in particular, booster vaccines are being promoted to the elderly to support cluster measures at facilities for the elderly. By doing so, the impact of infection can be reduced. "
Infections in children are increasing more than ever
According to the Ministry of Health, Labor and Welfare, the number of infected children under the age of 10 was 10,380 in the 5th wave, which was the highest in the week until August 31, 2021, but in the 6th wave, the number of infected children was decreasing. Even in the week leading up to March 15, 2022, the number of people continues to be high at around 65,000.
The proportion of children under the age of 10 in the total number of infected people was only about 5% in early January 2022, but since mid-February, the total number of infected people has been declining, and until the 15th of this month. The week is the highest in all age groups, accounting for 21% of the total.
The number of clusters related to children is increasing, and in the week leading up to the 14th of this month, the number of "child welfare facilities" such as nursery schools was 229, an increase of 56 from the previous week, the highest number ever, and "schools".・ Educational facilities, etc. ”has increased by 59 from the previous week to 318.
Experts say that Omicron strains are more likely to spread in groups such as schools and kindergartens than Delta strains, and the percentage of children vaccinated compared to other age groups. Points out that may be low.
(Chairman Takaji Wakita, Expert Meeting of the Ministry of Health, Labor and Welfare)
"Since the Omicron strain is highly infectious, the proportion of children who have not spread so far is high. It can be said from the infection situation by age group that the infection is not lower than other generations because it may not have been done. Currently, there are several areas where the infection has stopped or leveled off. However, where the rate of infection is high for teens and younger, the number of infected people has not decreased. There is no doubt that the infection of children is affecting it. It is spreading from the explosive infection of children like influenza. This is not the case, but there is a gradual spread from children to adults, and it has not led to a decrease. "
(Dr. Yoshihiro Takayama, Okinawa Prefectural Chubu Hospital)
"As a result of measures such as restrictions on restaurants, infections among young people have greatly decreased, but the effects of measures have not reached much for infections between children and infections that spread at home. The Omicron strain is more susceptible to upper airway infections and is more likely to be transmitted to children. It is also easier for children who complain of sore throat to access the test, so it is more likely to be transmitted to children. Isn't it also a factor that makes it easier to detect? "
(Professor Koji Wada, International University of Health and Welfare, member of the Ministry of Health, Labor and Welfare Experts' Meeting)
"In Japan, children under the age of 12 are in an age called'pocket'where vaccination has not progressed. Since there is no prospect of receiving vaccination, it is easy for the infection to spread. It is quite possible that the infection will remain in the children in the future, so the infection will spread to the children, especially from the new semester to around the summer. You should avoid closing nursery schools, kindergartens, and schools as much as possible, and you should secure opportunities for learning. People with symptoms should take a rest, but if there are no symptoms, infection control Support that can be operated while doing is important. "
There is a risk of re-expansion without decreasing
If there are more opportunities for contact with people at the three consecutive holidays from the 19th, the graduation ceremony at the end of the year, and the welcome and farewell party, there is a risk that the infection will spread again without being completely reduced.
A research group of Professor Akimasa Hirata of Nagoya Institute of Technology predicted using AI = artificial intelligence that the number of infected people in Tokyo would be almost flat after dropping to about 5,400 people a day in early April. became.
Professor Hirata's group uses AI to make predictions based on data such as human flow, past infection status, and vaccine effects.
▽ Assuming that the flow of people recovered to the same level in 2021 after the cancellation of priority measures such as prevention of spread, the number of newly infected people in Tokyo decreased to more than 5,400 people a day in early April, and then increased slightly. It is expected that the number of people will be almost flat, and even in late April, there will be more than 5,600 people a day.
▽ If the number of people increased by 20% from the same period in 2021, it will increase slowly after the beginning of April, and it is predicted that the number of people will increase to about 7,700 a day in the middle of April.
▽ If the number of drinking parties increases at the same level as the year-end and New Year holidays in addition to the increase in the number of people, the number of newly infected people will start to increase at the end of March, and it is predicted that there will be more than 13,000 people a day in mid-April. That is.
The group said that although it is unlikely that the number of severely ill patients will increase sharply considering the effects of the third vaccination, it may be necessary to take measures such as limiting the number of people who eat meals in order to prevent the re-spread of the infection. is.
(Professor Akimasa Hirata, Nagoya Institute of Technology)
"It can be said that this time is a time when the number of infected people is difficult to decrease because the number of people and banquets with a large number of people tends to increase."
Will it replace "BA.2"?
There is another concern.
It is a virus of the "BA.2" strain, one of the Omicron strains.
At the expert meeting of the Ministry of Health, Labor and Welfare held on March 15, the forecast of the future transition of "BA.2" in Japan was presented.
Among them, Professor Hiroshi Nishiura of Kyoto University predicted that 82% of all Omicron strains will be replaced with "BA.2" in Tokyo as of April 1, based on the inspection data of Tokyo. rice field.
In addition, according to the analysis presented by Motoi Suzuki, Director of the Epidemiology Center for Infectious Diseases, National Institute of Infectious Diseases, the percentage of "BA.2" nationwide is as follows, based on a sampling survey of two private testing institutions. Was expected.
70% as of the first week of April.
97% as of the first week of May.
It is believed that "BA.2" is about 20% more infectious than "BA.1", which is currently the mainstream.
If the replacement with "BA.2" progresses, there is a risk that the same measures as before will not be enough to suppress the infection.
(Chairman Takaji Wakita, Expert Meeting of the Ministry of Health, Labor and Welfare)
"There is a possibility that the number of infected people will turn to an increasing trend again due to the replacement of the" BA.1 "strain virus with the more infectious" BA.2 ". Yes, you need to be careful. "
What should I do in the future?
What should we do to prevent a major wave of infection and prevent medical strains in the future?
On March 17, after the basic coping policy subcommittee that approved the policy of canceling the priority measures, Chairman Shigeru Omi said, "If the priority measures are lifted, the number of infected people may increase, but the number of seriously ill people It is important to control it to some extent so that medical strains can be avoided. Even in Europe, where the vaccination rate is high, there are countries where the number of deaths is decreasing and some countries are increasing, and measures other than vaccines are in place. The country is relatively responsive. Vaccines are needed but not sufficient, and if infection control is not continued, deaths will increase as in some European countries. Small flies, infections with aerosols It's getting more and more, so it's better to still wear the mask to protect yourself and others, and I'm thinking of doing it too. "
Other experts will continue to pay attention to infection control, especially when vaccination is promoted and actions with a high risk of infection are taken, especially in the season when there are many events with many contacts with people. We are calling for careful measures.
(Professor Koji Wada, International University of Health and Welfare)
"Since the chances of getting infected will increase in the future, in order to protect not only yourself but also your family and friends, get the third vaccination as soon as possible, including young people. It is important to take measures against infection, such as viewing flowers with a small number of people such as family members, and allowing parents to participate in graduation ceremonies that do not eat or talk. It is important to tell the citizens and businesses what they want after the infection. "
(Professor Kenji Kutsuna, Osaka University)
" There is a possibility that the number will increase again in Tokyo and Osaka Prefecture after the priority measures are lifted. The next epidemic may come earlier than the interval. By the time the next wave arrives, the elderly will be given additional vaccinations, and the infected elderly will be intervened at an early stage. It is necessary to promptly establish a support system, such as starting treatment and providing early guidance on infection control. ”
(Professor Yoshihiro Takayama, Okinawa Prefectural Chubu Hospital)
“ The epidemic has occurred after the spring vacation for the past two years. Therefore, it is necessary to prepare for the possibility that the 7th wave will occur. If an infection is found in a facility for the elderly, intervene as soon as possible to prevent the spread and promote additional vaccination. By doing so, I hope to be able to overcome the 7th wave without imposing major restrictions on society as a whole. "