42% of Japan’s Population Has COVID Antibodies, Survey Finds

Yomiuri Shimbun file photo
An antibody test is performed in Natori, Miyagi Prefecture, in June 2020.

A health ministry survey has found that 42.3% of Japan’s population has acquired antibodies against the novel coronavirus, indicating past infection. This represents an increase of about 13 percentage points from the previous survey in November, due to this past winter’s eighth wave of infections.

There were regional differences in the percentages of people with antibodies, which can only be acquired through infection with the virus. Fukuoka, for example, had about double the figure seen in Iwate Prefecture. The survey also found the percentage decreased with age.

The survey was conducted by the Health, Labor and Welfare Ministry from Feb. 19 to 27 with the help of the Japanese Red Cross Society on about 13,121 men and women aged 16 to 69 who donated their blood around the country.

The preliminary figure was up from 28.6%, the finalized figure in the previous survey, but remained relatively low compared to the United States and European countries.

By prefecture, Fukuoka saw the highest percentage at 59.4%, followed by 58.0% in Okinawa, 52.5% in Saga and 51.8% in Aichi. Iwate had the lowest percentage at 27.4%, making it the only prefecture under the 30% mark.

In Tokyo, 42.2% of the population had antibodies, compared to 50.2% in Osaka.

By age group, people aged 16 to 19 had the highest percentage at 62.2%, while the figure was as low as 28.3% among those in their 60s.

Infection and vaccination are thought to heighten immunity to the virus. According to Tetsuya Matsumoto, a professor of infectious diseases at the International University of Health and Welfare, elderly people need to continue protecting themselves through vaccination and masks, because they have a higher risk of falling seriously ill if they catch the virus.