Based on the number of new coronavirus infections announced by local governments in each region, NHK summarized the trend of the number of new infections on average per week compared to the previous week, and the number of infected people nationwide is The lowest level has continued since entering.
On the other hand, in Tokyo and other areas, there is a tendency for the decline to stop, with a slight increase.
On the 12th, the government decided on the overall picture of countermeasures in preparation for the sixth wave of the new coronavirus.
"Will the 6th wave come?" "When will it come?"
We interviewed five experts.
Specializes in mathematical models (MHLW Cluster Countermeasures Group, Dr. Furuse)
"The sixth wave is likely to come this winter," said Furuse, a doctor who is an expert in infectious disease epidemiology using mathematical models and a member of the cluster countermeasures group of the Ministry of Health, Labor and Welfare. This is Yuki.
Mr. Furuse has been in charge of simulating the infection situation at expert meetings of the Ministry of Health, Labor and Welfare regarding the new corona.
What Mr. Furuse is doing is converting various factors related to the spread of the new corona, such as vaccination rate and people's behavior, into mathematical formulas and simulating the future infection situation.
The main assumptions used in the calculation are:
▽ Vaccine rate 90% for people in their 60s and over, 80% for people in their 40s and 50s, 75% for people in their 20s and 30s
▽ Vaccine effect is assumed to be 70% for infection prevention with two vaccinations
▽ Contact between people
As a result
of 80% (that is, 20% decrease) before the new corona
, the number of infected people, which was initially low, started to increase after one month and increased sharply after two months.
If you reduce contact with people, you can postpone the time of the 6th wave
According to Mr. Furuse, by reducing contact with people, the time when the sixth wave will come will be postponed.
However, in the simulation, even if the contact with people was suppressed to 60% (that is, reduced by 40%), the result was that a wave of epidemics would come in about 5 months.
This simulation does not include the third vaccination in the assumption, which means that if the third vaccination progresses in the future, the effect of the sixth wave will be smaller.
It is difficult to know exactly what level of contact people are currently in contact with each other, but Mr. Furuse points out that caution is required for the year-end and New Year holidays.
"In winter, it is known from past experience that respiratory infections are likely to spread. In addition, year-end parties are held and people are actively moving toward the end of the year and the beginning of the year with the feeling of being in front of the new corona. If this happens, the infection may spread again. On the other hand, some people are worried that their behavior is slowly slowing down, but many people wear masks and have fewer drinking parties. Life is getting closer to "new normal" and the chances of contact can be reduced by holding meetings online. If this situation continues, the sixth wave itself will be unavoidable, but the scale will be smaller. Then, we may be able to aim for a society where the strain on medical care can be avoided. "
Simulation with AI (Professor Hirata, Nagoya Institute of Technology)
There are also attempts to predict future infections using AI = artificial intelligence.
Professor Akimasa Hirata of Nagoya Institute of Technology trained AI to learn the infection data so far and simulated the situation in Tokyo in the future.
The data learned by AI has been diverse, including changes in the number of infected people, temperature, humidity, people flow, and whether or not a state of emergency has been declared.
I assumed that the flow of people would gradually return.
Then, we asked AI to perform 27 patterns of simulations with different conditions such as the vaccination rate and when to start the third vaccination.
"The sixth wave of epidemic mountains predicted by AI will inevitably come out in early January next year. Considering the latent period of the virus, how many people go out to play from Christmas to the year-end and New Year, family and relatives It depends on how much it spreads at the gathering in Japan. ”
No matter what pattern you calculate, the result is that the sixth wave will start toward the beginning of January.
However, if the third vaccination progressed, the number of infected people began to decrease at a relatively early stage, and the number of severely ill people could be kept low.
"The important thing is to keep the vaccine efficacy rate at a high level for the entire population, such as by giving a third vaccination. In Japan, vaccination has progressed rapidly, so the effectiveness of the vaccine will decline rapidly. There is a possibility. If we do not start the third vaccination, it will be difficult to maintain the effective rate. "
Specializes in public health such as infectious diseases (Professor Wada, International University of Health and Welfare)
Professor Koji Wada of the International University of Health and Welfare, who is a member of the expert meeting of the Ministry of Health, Labor and Welfare and specializes in public health such as infectious diseases, also warns that it is necessary to be careful when the number of people increases during the year-end and New Year holidays.
"If you look at seasonal factors such as cold and humidity and the relationship with the movement of people, it is the same for influenza, but be aware that the infection is most likely to spread during the year-end and New Year season when movement is active at year-end parties and New Year's parties. It is necessary. "
On top of that, regarding what the sixth wave will look like, how much the restrictions on social activities will be relaxed due to the progress of vaccination, how the effectiveness of the vaccine will decrease over time, etc. However, there are many parts that are not yet understood in detail, and it is difficult for even experts to make a judgment.
However, Mr. Wada points out that the sixth wave may be different from the fashion so far.
"For example, in the United Kingdom, where vaccination preceded, many infected people, mainly in their 30s and 50s, have been vaccinated. However, there are quite a few cases where vaccinated people become seriously ill. It is declining, and it seems that the effect of preventing serious illness is relatively continuing. Also, the number of infected people will increase in the teens and younger, when the proportion of vaccinated people is small, but this generation is originally less likely to become severely ill. The rate of aggravation should be quite low
, "said Professor Wada
."
Looking at the cases in each country, it is wrong that people who have not been vaccinated will be the main cause of the spread and aggravation of the infection in the future. No. In Tokyo, for example, one in five people in their 40s is not vaccinated. This winter, we will continue to inoculate the vaccine so that both individuals and the community can spend their time with peace of mind. I think it will be important. "
Infectious disease control specialist (Dr. Takayama, Okinawa Prefectural Chubu Hospital)
Dr. Yoshihiro Takayama of Okinawa Prefectural Chubu Hospital, who participates in the expert meeting of the Ministry of Health, Labor and Welfare as an expert on infectious disease control, is paying attention to the difference in the spread of infection between metropolitan areas and rural areas.
"Maybe the way of thinking changes between metropolitan areas and rural areas. In urban areas, there are spots where infections continue to smolder, and when people come into contact with each other, the infections ignite the fuses. There is a possibility that it will burn up. On the other hand, in rural areas, including Okinawa, the epidemic itself has subsided and infected people have not been confirmed in some places. In such places, it is important in urban areas. It is an influx of infections from other areas. We call on people from other areas to refrain from coming to the prefecture when there is a mechanism like a "vacuum / test package" or when a certain scale of outbreak occurs. It is very important to be able to do it. There is a sense of crisis in rural areas, so I try to call it enthusiastically, but this message is meaningless unless it is actively sent in the metropolitan area. Infection The number of people is decreasing, and it is difficult to get attention, but I would like you to call for it even in urban areas. ”In addition, Dr. Takayama pointed out the time when he should be wary of re-spreading the infection.
Measures should be taken while being wary of the spread of infection after the New Year
"Even if we take proper measures, it is thought that the infection will be brought to the rural areas to some extent during the year-end and New Year holidays. Especially, there are many elderly people in the rural areas who have not been able to meet their grandchildren for a long time, and this New Year is the same. There are many people who want to spend time with their families. It is important to take measures such as confirming that they are vaccinated so that they can spend time together. In urban areas, in December. The number of infected people will increase at year-end parties, etc., and then it will spread to rural areas during the year-end and New Year holidays, so we should take measures while being wary of the spread of infection after the New Year holidays. " is.
"Looking at the situation in Europe and the United States, we should think that an epidemic will occur in Japan this winter on a scale that surpasses this fifth wave. If the effectiveness of the vaccine declines over time, it will be better than this summer. It is possible that more elderly people will be hospitalized and unable to leave the hospital. Increasing the number of beds is limited, especially in rural areas, and it is very difficult during the winter months when there are already many common illnesses. It is very important to increase the number of facilities that accept patients and shorten the length of hospital stay. If the length of hospital stay can be halved, it will have the same effect as doubling the bed. I have to talk with the director of each hospital and get ready. "
Estimated by "Mini Tokyo" (Postdoctoral Fellow, The Tokyo Foundation for Policy Research, Chiba)
All the experts interviewed pointed out that the sixth wave could come during this winter.
So how do you deal with the sixth wave?
Asako Chiba, a postdoctoral researcher at the Tokyo Foundation for Policy Research, is also one of the concerns about the re-expansion of the infection this winter.
"I think that the 6th wave will occur when the effect of the vaccine decreases and the number of people increases." Mr. Chiba asked "Mini Tokyo" how to keep the 6th wave as small as possible. I'm trying to figure it out with the simulation I used.
Based on data such as the national census, we will simulate the spread of infection assuming a so-called "mini Tokyo" with a population of about 70,000, whose age composition, occupation, family composition, etc. are very similar to those of the actual Tokyo. I did it.
In the simulation, the number of newly infected people per day was assumed to be 4 in "Mini Tokyo".
When applied to actual Tokyo, it will be about 800 people.
The time is assumed to be after October.
As a result, it was calculated that if the number of people remained 30% less than before Corona, the number of infected people would level off even if the vaccine's effect declined.
Furthermore, if the third vaccination progresses, the number of infected people is expected to decrease.
* "Attenuation" in the graph = Attenuation of vaccine effect
Next, if the rate of decrease in the number of people is reduced to 20%, the number of infected people will tend to increase even if the third vaccination is assumed. It was the result.
"Even if the number of people increases a little, it is possible that the infection situation will be completely different. In the future, if the whole world becomes like holding a year-end party, the infection may increase overall. However, considering the economy, it may be difficult to keep the number of people reduced uniformly. ”
Therefore, Mr. Chiba pays attention to the fact that he has been vaccinated and the test is negative. It is to make good use of "vaccine / test packages", etc., where behavioral restrictions are relaxed by proving.
According to Mr. Chiba's simulation, even if the number of people who received the vaccine returns to the level before Corona, if the number of other people decreases by 50%, the number of infected people will tend to decrease. It means that it became a calculation.
"It is certain that controlling the flow of people in the entire population will be effective, but when considering compatibility with the economy, it will suppress the behavior of people at high risk of infection, such as not being vaccinated. That is also very effective. We should discuss what kind of policy such as vaccine / test package is effective. "
How to avoid hitting the "sixth wave of this winter" prediction
In this interview, many experts said that increasing "people-to-people contact" is the key to predicting when and when the sixth wave will come.
In addition, Shigeru Omi, chairman of the government subcommittee on measures against the new corona, and Takaji Wakita, chairman of the expert meeting of the Ministry of Health, Labor and Welfare, also created a place to continue wearing masks and becoming dense even if the number of infected people decreases at press conferences. After calling for the continuation of basic infection control measures such as thorough "zero density", we are calling for caution against increasing contact between people toward the end of the year and the beginning of the year.
As Professor Koji Wada of the International University of Health and Welfare interviewed this time, it is not easy to predict whether or not the infection will spread because various factors affect each other in a complex manner.
Nevertheless, there are some factors that will be a light of hope, such as vaccination and the development of new therapeutic agents.
It is important to continue to take various measures while making use of the experience up to the 5th wave so that the prediction that "the 6th wave will come this winter" will not hit as much as possible.