As athletes parade into Tokyo’s Olympic stadium to mark the official commencement of the Summer Games, medical officials have revealed that about 100 U.S. Olympic athletes in Tokyo are unvaccinated. 

Of the 613 American athletes descending to Japan's capital, 567 filled out their health histories before the trip. An estimated 83% had replied that they were vaccinated, according to the U.S. Olympic and Paralympic Committee’s medical chief Dr. Jonathan Finnoff. 

“Eighty-three percent is actually a substantial number and we’re quite happy with it,” Finnoff told AP News.

This estimate is higher than the overall vaccination rate in the U.S. where only 48.8% are fully vaccinated, the Centers for Disease Control and Prevention data shows. 

So far, two U.S. athletes have tested positive for COVID-19 ---beach volleyball player Taylor Crabb and gymnastics team alternate Kara Eaker.

Overall, the International Olympic Committee has reported 13 positive cases among all athletes in the Tokyo Games. 

The IOC does not require athletes to be vaccinated in order to participate but it had “received assurances” that at least 85% of delegates had been vaccinated, it told Forbes. 

The Committee partnered with Pfizer and BioNTech in early May to donate vaccine doses to Olympians before they descended to Tokyo.

However, some athletes refused to get the vaccine, fearing side effects would hinder their performance, while others were skeptical overall. Some were never able to access the vaccine at all, despite the IOC’s efforts.