Updated

The Tokyo Olympics opened Friday under a cloud of uncertainty as the coronavirus pandemic still hangs over the entire world with some athletes contracting the illness even before the Games got underway.

The U.S. Olympic and Paralympic Committee (USOPC) said about 100 of the 613 U.S. athletes in Tokyo for the Olympics remain unvaccinated. USOPC medical director Dr. Jonathan Finnoff said 567 athletes have filled out their health histories and a resounding majority replied they were vaccinated.

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"Eighty-three percent is actually a substantial number and we're quite happy with it," Finnoff said.

The International Olympic Committee estimated that about 85% of residents in the Olympic Village were vaccinated. The number is based on the reports from each country’s Olympic committee but is not an independently verified number.

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Finnoff said the U.S. wasn’t differentiating its treatment of athletes based on vaccination status.

"The best thing to do is to assume everyone's at risk, and reduce risk by introducing COVID mitigation measures that we know work," he said.

So far, only two American athletes are known to have tested positive for the coronavirus while in Japan – beach volleyball player Taylor Crabb and alternate gymnast Kara Eaker.

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The coronavirus pandemic pushed the start of the Tokyo Games back a year. Organizers determined at the last minute that domestic fans were to be banned from attending the Games.

The Associated Press contributed to this report.