Japan will test around 10,000 people for coronavirus antibodies starting from next month, as part of efforts to better understand the deadly infection, health minister Katsunobu Kato said Friday.

The tests, which look for specific proteins made by the immune system in response to the infection, will likely take in place in Tokyo and Osaka, among other prefectures, officials said. Potential areas include those that have reported a relatively high number of infections and those with fewer cases.

Testing is expected to help authorities grasp the extent to which the virus has spread in those regions, how many people will need a vaccination when one becomes available, and the outlook for infection numbers should there be a second wave.

It will also help determine whether Japan is on the way to herd immunity, achieved when a large portion of the population develops antibodies and protection from infection.

The tests use a blood sample and take less time than the currently dominant polymerase chain reaction test, which uses a swab from a patient's nose and requires a minimum of several hours to produce a result.

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

The tests come after the ministry last month conducted experimental screening for antibodies in donated blood in Tokyo and six prefectures in northeastern Japan, using test kits from five firms.

It found 0.6 percent of 500 samples from Tokyo had antibodies for coronavirus and 0.4 percent in the same number of samples from Aomori, Akita, Iwate, Miyagi, Yamagata and Fukushima.

But experts noted some of the test kits could have provided false results. In the screening, two samples of blood donated last year -- before coronavirus was confirmed in Japan -- tested positive for antibodies.

The first case of the contagious respiratory disease was identified in Wuhan, China, late last year.

It typically takes one to three weeks for the development of antibodies after someone becomes infected with SARS-CoV-2, the coronavirus that develops into COVID-19, according to the U.S. Centers for Disease Control and Prevention.

There are various types of antibody test kits available for COVID-19 but doubts remain over their accuracy.

Kenji Mizumoto, a project assistant professor with expertise in infectious disease epidemiology at Kyoto University, said the screening would assist efforts to get a large picture of infections in the country, rather than numbers of infected people.

Related coverage:

Osaka to remove part of business suspension requests from Saturday

FOCUS: Japan-style virus fight still halfway despite easing of emergency

Japan lifts coronavirus emergency outside Tokyo, Osaka regions