Japan will start testing 10,000 people in Tokyo, Osaka and the northeastern prefecture of Miyagi for antibodies of the coronavirus from early June as part of efforts to better understand its spread, health minister Katsunobu Kato said Friday.

Authorities hope to grasp the rough number of people in those areas who have been infected with the virus, including those who have not shown any symptoms, as well as gain an outlook for infection numbers should there be a resurgence.

(Mirimus, Inc. lab scientists work to validate rapid IgM/IgG antibody tests of COVID-19 samples from recovered patients on April 10, 2020 in the Brooklyn borough of New York City.)
[Getty/Kyodo]

The results will also help authorities estimate how many people will need vaccination.

"We will confirm how much immunity the entire community has acquired and utilize the data to prevent the virus spreading in the future," Kato said at a press conference.

The government has chosen the three prefectures as Tokyo and Osaka have high rates of confirmed infections, measured in the number of people testing positive per 100,000 people, while Miyagi has a relatively low rate.

The blood tests, which look for specific proteins made by the immune system in response to infection, will be conducted on roughly 3,000 adults randomly selected in each of the three regions who consent to take part.

Local authorities will conduct the tests and send blood samples to the central government for analysis. The state will leave it up to the municipalities whether to inform the examinees of the results.

The Ministry of Health, Labor and Welfare plans to use several methods to find antibodies and figure out the amount of antibodies in specimens, ministry officials said.

It typically takes one to three weeks for the development of antibodies after someone becomes infected with the virus that causes the COVID-19 respiratory illness, according to the U.S. Centers for Disease Control and Prevention.