Japan's health ministry has estimated that about 40 percent of people across the country as of last month had a type of coronavirus antibody which can only be acquired through infection.

The ministry made the calculation by examining blood samples taken from 13,121 individuals between the ages of 16 and 69 in late February.

It found the antibody in 42.3 percent of the samples. That was up roughly 14 percentage points from November, when the nation was entering the eighth wave of infections.

The proportion tended to be lower in older groups. People aged 16 to 19 had the highest ratio at 62.2 percent, compared to 28.3 percent among those in their 60s.

The figure in Tokyo was 42.2 percent while Osaka's ratio was 50.2 percent.

The head of the ministry's expert panel, Wakita Takaji, said Japan's antibody prevalence rate remains lower than those of Western countries.

He added that there is a need to continue tracking relevant data as Japan's relatively low figure could affect its future infection situation.