The number of people infected with the new coronavirus per day reached a record high of 186,000 on July 21st.


"The spread of the infection is still going on. Probably no immediate peak out," Shigeru Omi, chairman of the government subcommittee, told NHK in an interview.


One of the Omicron strains, "BA.5," is thought to be significantly involved in the "7th wave" of the spread of infection.



What is the infectivity and severity of infection?


How far will it expand in the future?


I have summarized what I have learned.

"BA.5" in the background of "7th wave", the highest number ever

It is believed that the progress of replacement of the " 7th wave"



Omicron strain, which has become the most infected in the past, with "BA.5" is a major factor in the expansion.

Shigeru Omi, chairman of the government subcommittee, said that the background of "7th wave" is that the infectivity of "

BA.5


" is higher than that of the conventional Omicron strain.


"Immune escape"


▽ The effect of immunity has decreased several months after the


third vaccination ▽ The fourth vaccination of the elderly is still in progress, and the vaccination rate of the younger age group may still be low.


I pointed out.



"The spread of the infection is still going on. I think it's likely that the peak out will not happen soon and it's safe to double the peak of the 6th wave," said Omi. rice field.

New Corona Record-highest number of infections in the summer of rapid spread How to ask Chairman Omi

What is the infectivity of "BA.5"?

"BA.5" is a type of Omicron strain, which was confirmed in South Africa in February 2022, and has spread mainly in Europe and the United States since May.



Currently, most of the new coronaviruses detected in the world are Omicron strains, and according to WHO = World Health Organization, "BA.5" increased by 2 points from the previous week to 53.6% in the week until July 10. Occupies.



In the United States, the week leading up to July 16 accounts for 77.9% of the total.



WHO Secretary-General Tedros said at a press conference on July 19, "The number of infected people in the world has almost doubled in the last six weeks. The number of deaths has not increased as much as the number of infected people, but in the future As the number of infected people increases for several weeks, the number of hospitalizations and deaths is expected to increase. "



He also says he "BA.5 is the most infectious mutant virus ever detected."



According to a statement released by the British health authorities on June 24, "BA.5" is expected to spread 35.1% faster than "BA.2".

According to an analysis by the National Institute of Infectious Diseases, the proportion of "BA.5" in the country is estimated to be 96% as of this week, and it is estimated that it will be 100% nationwide in the first week of August. It is supposed to be.



According to the materials presented by Professor Hiroshi Nishiura of Kyoto University at the expert meeting of the Ministry of Health, Labor and Welfare, as a result of analysis based on the data in Tokyo, "BA.5" is compared with "BA.2" which was the mainstream until now. It is estimated that it is spreading 27% faster.

The characteristic of escaping immunity

"BA.5" is a protrusion on the surface of the virus, and mutations called "L452R" and "F486V" have occurred in the "spiked protein" that serves as a foothold when infecting cells.



It is believed that these mutations have led to the ability of "BA.5" to escape immunity.



According to WHO, "BA.5" has an experimental result that the effect of the neutralizing antibody that suppresses the action of the virus is less than one-seventh that of "BA.1" that initially spread.



In addition, according to a paper published in the scientific journal "Nature" on July 5, a group of Columbia University in the United States, in an experiment using blood such as a person who was vaccinated with the mRNA vaccine of the new corona three times, "BA.4 "" And "BA.5" means that the effect of the neutralizing antibody was less than one-fourth that of "BA.2".



Furthermore, the weakening of immunity obtained by vaccination and infection over time is thought to have contributed to the spread of infection.

According to the estimation data presented by Professor Nishiura of Kyoto University at the expert meeting of the Ministry of Health, Labor and Welfare on July 21, the percentage of people who are immune to "BA.4" and "BA.5" of the Omicron strain will be. It means that it is falling even in the age of.

As of July 20, the percentage of people with immunity was


30.1% in their 20s ▽


29.2% in their 30s ▽


28.0% in their 40s ▽


28.6% in their 50s ▽


25.4% in their 60s


▽ 25.1 in their 70s and above %


And so on.



Professor Nishiura said in mid-July, "It is thought that a considerable proportion of people are vulnerable to" BA.4 "and" BA.5 ". Breakthrough infection and reinfection are likely to occur. It's a situation. "

What about reinfection?

On the other hand, WHO stated in a weekly report issued on July 20 that "people who were previously infected with'BA.2'will be protected from infection" regarding the risk of re-infection, before peer review in the Middle East and Qatar. The research results of the paper are quoted.



According to this, the effect of preventing reinfection with "BA.4" and "BA.5" was


as low as 28.3% for those infected with the new coronavirus before the


Omicron strain, whereas the "BA" of the Omicron strain was low.

It is said that 79.7% of the people infected with ".1" or "BA.2"


.



According to the research group, "People infected with" BA.1 "or" BA.2 "have a strong effect of being protected against" BA.4 "and" BA.5 "."

Is it easy to get serious?

In a weekly report issued on July 20, WHO said, "Scientific research results obtained so far show that there is a difference in severity compared to'BA.2'" regarding whether or not it is likely to become severe when infected. It is not recognized as being. "



On the other hand, "BA.5" has been reported in 100 countries, and it is said that the number of infected people and the number of people who have been hospitalized or treated in the intensive care unit are increasing.



The ECDC = European Centers for Disease Control and Prevention also said, "There is no evidence that the severity is increasing," and points out that as the number of infected people increases, the number of hospitalizations and deaths may increase. ..

Atsuo Hamada, a specially appointed professor at Tokyo Medical University who is familiar with overseas infectious diseases, said, "In Europe, the infection of" BA.5 "has spread a little earlier than in Japan, and the situation in Western Europe such as France, Italy, and Germany is I think it will be useful for Japan in the future. So far, the number of infected people is increasing, but the number of severely ill people is not so increasing. As the total number of infected people increases, especially the elderly. We are worried that the number of seriously ill people will increase, especially in Japan. "

What is the effect of the medicine?

Does the existing medicine work for "BA.5"?



On July 20, new research results were reported.

A group of Yoshihiro Kawaoka, a specially appointed professor at the Institute of Medical Sciences, the University of Tokyo, infects cultured cells with an actual virus and investigates the extent to which the growth of the virus can be suppressed by therapeutic agents. Published in "New England Journal of Medicine".

According to this, the components of "remdesivir" administered by intravenous drip, "Lagebrio", which is a drug for drinking, and "Pakirovid", which is another drug for drinking, are more effective in suppressing the growth of the virus than "BA.2". It was expensive.



On the other hand, some therapeutic drugs using antibodies were significantly less effective than the original effects on the virus.



Professor Kawaoka said, "The pathogenicity of'BA.5'is not yet fully understood, but in the experiments, even drugs that can be used in Japan were highly effective, so I think it is safe in that respect."

What is the effect of the vaccine?

Regarding vaccines, UK health officials provided analysis of initial data in a report issued on June 24.


According to this, when we analyzed the data of people infected during the month until the end of May, the effect of the vaccine on people infected with "BA.5" was on people infected with "BA.2". It reports that there was no significant difference compared to the effect.



In addition, on July 19, a group at the University of Washington in the United States artificially created a virus that reproduced the characteristics of "BA.5" in the science magazine "Science" and neutralized it using the blood of a person vaccinated with an mRNA vaccine. We reported the result of investigating the function of the antibody.



The effect of the neutralizing antibody was less than 1/23 of the virus that was the mainstream in the past with 2 inoculations, but it was about 1/6 with 3 inoculations.



According to the group, "In" BA.5 ", the effect of the vaccine is considerably reduced by the second inoculation, but by the third booster inoculation, it can be restored to the same level as the effect on" BA.1 "." ..



On the other hand, the US FDA = Food and Drug Administration announced on June 30 that booster vaccines to be given after this fall will be "BA.4" and "BA.5" in addition to the components of the vaccine currently in use. It announced that it recommended to pharmaceutical companies that it should develop a product with the addition of booster protein.



However, the current vaccine will be the basis for preventing the disease from becoming severe when infected with the new corona, and it does not require changes to the current vaccination.

Professor Hamada of Tokyo Medical University said, "We have not yet obtained data on the effectiveness of the vaccine, but at least two vaccinations are not very effective. A third vaccination will prevent infection to some extent. It is important that it is effective and that the effect of preventing aggravation remains for nearly half a year after vaccination. It is important to further improve the effect of preventing aggravation by giving a fourth vaccination. The spread of infection after the fall may be more serious than it is now. Discussions should be held at the national level on the concept of vaccination after the fall and the securing of vaccines. "

How far has the infection spread?

Professor Akimasa Hirata of Nagoya Institute of Technology shows the results of prediction of the number of infected people and deaths in the future analyzed using AI = artificial intelligence.



Assuming that the infectivity of "BA.5" is 1.3 times higher than before, based on data such as changes in the number of infected people in the past, the effects of vaccines, and the flow of people, based on the recent rapid spread of infection. Calculated as of July 15th.

As a result, the number of infected people in Tokyo peaked on July 27, and the average number of infected people per day per week was about 20,000, and the maximum was about 23,000. ..



However, Professor Hirata said, "It is possible that AI is learning the tendency that if the number of infected people increases too much, the tests will not catch up and the number of reported infected people will level off," and the infection can spread further. Gender cannot be denied.



On the other hand, the number of seriously ill people is about 60 per day in mid-August in Tokyo, and the number of people who die is about 26 per day in mid-August.



Professor Hamada of Tokyo Medical University said, "Infection control was considerably relaxed in Japan throughout June, and" BA.5 "spread in Japan at that time, so the infection spread mainly in the dining scene. It is thought that this led to a rapid increase in the number of infected people in early July. I think that there are many people who have realized the rapid increase in infected people and are tightening their actions. , I think it's very important to bring the "7th wave" epidemic to the peak out early. "