TOKYO -- Less than 1% of people in five prefectures across Japan were found to have coronavirus antibodies in tests conducted at the end of 2020 by the health ministry on a total of about 15,000 individuals.
The Ministry of Health, Labor and Welfare broke down the results of their tests by prefecture, with 0.91% of people in Tokyo testing positive for antibodies, 0.58% in Osaka, 0.14% in Miyagi, 0.54% in Aichi and 0.19% in Fukuoka.
At a press conference, health minister Norihisa Tamura said, "Although there are differences between each prefectural government, all of them had results lower than 1%. This is not herd immunity, so I ask people to continue providing their cooperation against infections."
The tests were conducted from Dec. 14 to 25, 2020, with each of the five participating prefectures choosing around 3,000 people at random as samples. Authorities used two different testing methods approved for use in emergencies by the U.S. Food and Drug Administration. Individuals testing positive under both methods were recorded as positive in the final results.
The number of individuals who met the criteria to test positive were 31 in Tokyo, 16 in Osaka Prefecture, four in Miyagi Prefecture, 16 in Aichi Prefecture and six in Fukuoka Prefecture. In the case of Tokyo, the latest antibody rate represented three times the infection rate in the capital (0.316%) calculated based on the accumulated number of infections as of Dec. 7, 2020.
Antibodies are proteins created by immune cells at times such as when a virus enters the body, and their presence in the blood can confirm whether a person has been previously infected. But there are a number of unknowns, such as how long antibodies can survive in the body and what level of immunity they afford against the virus.
A previous round of tests conducted in three prefectures in June 2020 found antibody rates of just 0.1% of people, or two individuals, in Tokyo, five people, or 0.17%, in Osaka Prefecture, and 0.03% of people -- a single person -- tested in Miyagi Prefecture.
(Japanese original by Hidenori Yazawa, Lifestyle and Medical News Department)