A health ministry survey has found that 42.3% of Japan's population has acquired antibodies against the novel coronaviruses, indicating past infection. This past winter's eighth wave of infections has resulted in an increase of about 13 percentage points from the previous survey in November.
There were regional differences in the percentages of people with antibodies that can only be acquired through infection with the virus. Fukuoka, for example, had more than double the figure seen in Iwate Prefecture. 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 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.
In the 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.
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 increase immunity to the virus. According to Tetsuya Matsumoto, professor of infectious diseases at the International University of Health and Welfare, elderly people need to protect themselves through vaccination and masks because they have a higher risk of contracting serious illness if they catch the virus.