Tokyo Finds Residents With Virus Antibodies at a Fraction of NYC

(Bloomberg) -- Only 0.1% of people in Tokyo tested positive for antibodies against the coronavirus, a survey conducted by Japan’s Health Ministry found, indicating the spread of the virus in the nation’s capital remains limited even though the number of cases may be higher than those already found.

The survey involved 1,971 participants in Tokyo. Japan’s decision to limit testing for the virus, an approach it says helped prevent the spread of the disease, has left many wondering what the true infection rate in the country is.

The antibody results, which indicate exposure to the virus, are far lower than those seen in Western cities that became hot spots in the global pandemic. A surveillance study carried out for the U.K. suggested 17% of Londoners had Covid-19 antibodies, based on results announced May 22, while on the same day in New York City, antibody tests found 20% of the population were positive.

Japan also conducted antibody tests in Osaka, where it found a 0.17% positive rate among 2,970 people, and Miyagi prefecture, where the rate was just 0.03% among 3,009 people surveyed. The surveys were conducted between June 1 and 7, and required antibodies to be identified by two separate tests made by Roche Holding AG and Abbott Laboratories for the result to be considered positive.

If the sample in Tokyo is representative of the general population, it would mean around 14,000 cases in the capital, compared to the more than 5,000 cases identified so far.

LocationPositive RateCases as of May 31Cases Identified as Percentage of Population
Tokyo0.10%5,2360.038%
Osaka0.17%1,7830.02%
Miyagi0.03%880.004%

In the largest antibody test undertaken so far in Japan, Softbank Group Corp. found 191 cases among 40,000 employees and families and medical workers. The result was a positive test rate of 0.43%, with only eight of more than 19,000 workers at its stores having been in contact with the virus.

Japan had conducted 340,000 PCR tests for the coronavirus as of Monday, the Health Ministry said, versus the more than 23 million tests taken in the U.S. Japan, a country of 126.5 million people, has identified around 17,500 cases.

One of the key architects of the country’s virus strategy, Professor Hitoshi Oshitani, earlier this month defended the country’s stance toward testing, saying that deliberately limiting access to PCR tests was a key reason for success by preventing waiting rooms from turning into breeding grounds for the virus. He also questioned the quality of PCR test kits used in the U.S. that were “prematurely” approved.

Japan’s Health Ministry cautioned the latest tests could not determine the nature of the antibodies, such as how long they remain in the body, or whether the presence of antibodies protects people from getting infected again.

©2020 Bloomberg L.P.

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