Corona-infected persons What is the possibility of leading to the increasing trend "7th wave" nationwide?

The number of new infections with the new coronavirus seems to have started to increase in various places such as the Tokyo metropolitan area from around last week in late June.

The number of infected people nationwide has also increased compared to the previous week.

The spread of infection has been repeated so far, but will it lead to the "7th wave"?

Experts say, "I don't know if it will lead to a major epidemic, but we should be careful about replacing it with a new mutant virus, and we need to temporarily raise awareness of infection control."

Newly infected people are increasing from the previous week, the highest number ever in Shimane

The number of newly infected people nationwide increased temporarily after the end of the long holidays, and has been on a downward trend since mid-May, but the number of newly infected people in a week compared to the previous week has been on an increasing trend since last week. By June 29, it was 1.17 times the previous week.

In Tokyo, the number of newly infected people by June 30 has increased 1.40 times compared to the previous week, and the number is increasing in the populous metropolitan area, Tokai, Kansai, and Kyushu.

In addition, in Shimane Prefecture, a large-scale cluster occurred at the Izumo City office, and on June 28, 305 people were confirmed to be infected, the highest number ever per day.

Evaluation of infection status Increased description of "increasing factors"

An expert meeting of the Ministry of Health, Labor and Welfare has stated that there are factors that lead to an increase in infection and factors that lead to control, and that the balance affects the status of infection.

Infection status assessment documents, which are issued after each meeting, are increasingly describing the factors that lead to the increase.

Specific factors cited by the expert meeting are that the immunity obtained by vaccination and infection is weakening over time, and that the number of people in downtown areas at night is increasing, and that in Tokyo. However, there are some areas where the peak is the same as or higher than the peak at the end of last year, such as an increase of 35% or more compared to just before the priority measures such as spread prevention were lifted in March, and the temperature rise and rainy days. The more you have, the more indoor activity you have.

Vaccine efficacy decreases over time

Currently, it is known that the effectiveness of the vaccine decreases over time for the Omicron strain, which is the main cause of infection.

According to data from the British health authorities, for example, if Pfizer is vaccinated twice and Pfizer or Moderna is vaccinated a third time, the effect of preventing the onset of the new coronavirus is 2 to 4 weeks after the third vaccination. After that, it is about 70%, but after about 3 months it will drop to about 50%, and after about 4 months it will drop to about 30%.

On the other hand, it is said that the effect of preventing infection from worsening symptoms and leading to hospitalization is 70% even more than half a year after the third inoculation.

Experts say that the effect of preventing infection will decrease in the future from those who received the vaccination earlier, and that the effect of immunity acquired by infection with the new coronavirus will gradually decrease in the future. increase.

Replacement with "BA.5" Needed to be monitored

Until now, the infection has spread by replacing it with a more infectious mutant virus, but in Japan, the Omicron strain "BA.2" has almost all of it.

However, "BA.5", which has become mainstream in the United States and is pointed out to be more likely to spread, is being detected in community-acquired infections, and it is expected that it will be replaced in the future. It is necessary to continue to monitor trends.

Atsuro Hamada, a specially appointed professor at Tokyo Medical University who is familiar with infectious diseases, said, "Although the number of detections of" BA.5 "is still limited, the number of clusters is increasing in various places such as Shimane Prefecture." BA.5 "in the United States and the Middle East. The replacement with ”is progressing considerably, and it is necessary to be careful in Japan in the future as the border measures are relaxed."

Increase / decrease on a relatively small scale Repeat

In the "6th wave", after the spread of Omicron strains caused the spread of infection on an unprecedented scale, it has been on a downward trend since mid-February.

However, during this period, it has been increasing for about 20 days from the end of March and for a week or so in the middle of May, and the increase and decrease on a relatively small scale has been repeated.

Also, I am concerned about the infection of the younger generation, who are active.

Since mid-June, the proportion of infected people in their 20s has increased by more than 20% in Tokyo and other areas.

With the spread of infection so far, there has been a tendency for the scale of infection to increase in the form of spreading to other generations such as the elderly after spreading through eating and drinking places in the younger generation.

"I don't know if it will lead to the" 7th wave ", but take measures."

This time, it has been about a week since the increasing trend started, but Professor Hamada points out that it is necessary to carefully watch the transition in the next few weeks, whether it will continue in the future.

Professor Hamada said, "I don't know yet whether this increase is temporary or will lead to the" 7th wave. "In addition to the decrease in vaccine effect over time and the relaxation of countermeasures, the recent rapid rise in temperature. The lack of ventilation and increased indoor activity can also be a factor in the increase. In order to keep the increase only temporarily, we asked them to strengthen their awareness of infection control for a short period of time, and even in the heat of the heat, they suffered from heat stroke. Ventilate as much as possible while avoiding it, and take basic measures such as refraining from contact if you are not feeling well. In particular, elderly people should take a fourth vaccination to prevent aggravation. " I'm talking.