1 In 4 Japanese Infected With Covid-19, According To Government Antibodies Survey

Source (Japanese): [https://news.yahoo.co.jp/byline/kutsunasatoshi/20221203-00326683](https://news.yahoo.co.jp/byline/kutsunasatoshi/20221203-00326683)

DeepL translation as follows:

Author: Kenshi Kutsuna

The Ministry of Health, Labour and Welfare’s Advisory Board on Countermeasures to Combat New Coronavirus Infections reported the results of a survey on antibody positivity rates in Japan.

The results indicate that approximately one in four people living in Japan and one in two people in Okinawa Prefecture are already infected with the novel corona.

What else can we learn from the results of this survey?

**What is the outline of this antibody survey?**

In this survey, antibodies called N antibodies were measured in 8260 people aged 16-69 who donated blood at the Japanese Red Cross Society in November 2022.

There are two major types of antibodies against new coronas, S antibodies and N antibodies. S antibodies are positive in both vaccinated and infected people, while N antibodies are positive only in infected people.

In this study, N antibodies are being measured for the purpose of surveying “people who have been infected with the new corona in the past.

**26.5% of people in Japan have been infected with the new corona in the past.**

The results of the N-antibody survey of blood donors indicated that 26.5%, or approximately one in four, had been infected with the novel corona in the past.

By prefecture, Okinawa (46.6%), Osaka (40.7%), and Kyoto (34.9%) had high rates, while Nagano (9.0%), Tokushima (13.1%), and Ehime (14.4%) had low rates. In Tokyo, 31.8% were positive.

This means that approximately one out of every two persons aged 16-69 in Okinawa Prefecture has already been infected with the new corona.

These results basically correlate with the number of infected persons per population in each prefecture reported so far.

In addition, by age, the positive rates of N-antibodies are:

* 16-19 years old: 38.0%
* 20-29 years old: 35.7
* 30-39 years old: 33.6%
* 40-49 years old: 26.8%
* 50-59 years old: 21.3%
* 60-69 years old: 16.5%

This means that one out of every three persons in their under 30s and one out of every four to five persons in their 40s or older have been infected with the new corona.

There was no difference in the prevalence between males and females.

So what do these results tell us?

**Millions of people are infected without being aware of it or being diagnosed.**

The survey was conducted on blood donors aged 16-69, so it is not representative of the entire Japanese population.

With that in mind, if we assume that roughly 1 in 4 people are infected, that means 33 million people in Japan are infected.

By December 3, 2022, 25 million people in Japan will have been diagnosed with the new coronas, so even if we subtract the fact that some people have been reinfected, it is estimated that several million people are infected but have not been diagnosed.

According to an overseas report, about half of those infected with the Omicron strain were unaware that they had been infected, so when combined with the results of this antibody survey, we can assume that there are many people in Japan who are infected without being aware of it.

**The number of infected people has increased rapidly after the Omicron strain.**

The government has conducted antibody surveys in the past, and this is the fifth time.

Although the same test system has not been used each time, it is thought to generally reflect the percentage of infected persons in the past.

According to previous reports, the antibody-positive rate has gradually increased with each survey, and 4.27% of all respondents were positive in the fourth survey conducted in February 2022, in the middle of the sixth wave of Omicron strain infections.

By the fifth survey, nine months later from that point, the rate had risen by more than 20%, and by 2022, the rate had risen by another 24%.

This means that approximately one in four people in Japan have been infected with the new corona since 2022.

This clearly shows how highly infectious the Omicron strain is.

Although people vaccinated with conventional mRNA vaccines are less likely to become infected with the omicron strain, it is becoming increasingly difficult to prevent infection completely.

On the other hand, people infected with the Omicron strain are known to be less susceptible to infection with new coronaviruses of the same Omicron strain, and these 24% are considered to be less likely to be reinfected, at least in the short term.

Currently, the number of new cases of novel coronavirus infection is increasing nationwide, but varies widely from region to region.

For example, the current epidemic situation differs greatly between Nagano Prefecture, where the antibody-positive rate was the lowest, and Okinawa Prefecture, where it was the highest.

In Nagano Prefecture, the number of newly infected cases has already exceeded the seventh wave, while in Okinawa Prefecture, the number of newly infected cases has increased only slightly since October.

Of course, this difference in the number of newly infected persons cannot be explained by the antibody positivity rate alone, but is related to various factors such as differences in temperature and humidity, ventilation conditions, and local vaccination rates, but the percentage of people who have been infected in the past is definitely an important factor in the current epidemic situation. However, there is no doubt that the proportion of people who have been infected in the past is an important factor in the current epidemic.

So how does this antibody-positive rate compare with that of other countries?

As an example, let us compare it to the United Kingdom, where antibody positivity rates are regularly reported.

In the United Kingdom, too, the antibody-positive rate among blood donors is regularly surveyed, and the current N antibody-positive rate in the United Kingdom is over 80%.

This means that 80% of the UK population has already been infected with the new corona, and since the Omicron strain has risen from 20% to 80% since its spread, the majority have been infected since the Omicron outbreak.

In the UK, the positive rate of S antibodies also exceeded 90% by mid-2021, which means that most people are vaccinated and another 80% are infected.

It is believed that vaccinated people who become infected will have stronger immunity, known as hybrid immunity.

The United Kingdom is currently in a situation where more people have this hybrid immunity, and it is thought that even if fewer people wear masks, the infection is less likely to spread.

It will take some time for Japan to reach this situation.

However, the United Kingdom has not reached this situation unscathed.

The number of deaths from new coronas per capita in the United Kingdom and Japan is approximately eight times greater.

The UK has suffered more damage than Japan.

It will be extremely difficult for Japan to increase the number of people with hybrid immunity while minimizing the damage, but in order to do so, it is important not to create a rapid increase in the number of infected people (keep the epidemic as small as possible) and to keep people at high risk of serious illness updated with vaccinations. This will be the case.

Although we may envy the situation overseas that seems to have returned to the pre-Corona era, it is important to proceed with mitigation at a pace appropriate for Japan, as “other places are different, and we are different.

Reference: 108th Meeting of the Advisory Board on Countermeasures to Combat New Coronavirus Infections (November 30, 2022), “Survey on the Antibody Possession Rate of New Coronaviruses Using Residual Blood Samples for Testing at Blood Donation (Preliminary Results, Summary)”.

Note: Since N antibodies can become negative over time, the positivity rate in this survey may have been estimated to be low. Also, as noted in the text, the antibody positivity rates for children under 16 years old and the elderly over 70 years old are not clarified in this survey.

Translated with [www.DeepL.com/Translator](https://www.DeepL.com/Translator) (free version)

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