The heir to the Danish throne, who has been vaccinated, was to travel to Japan on July 19 and attend the International Olympic Committee General Assembly July 20 and 21, along with the July 23 ceremony. He'll attend the former event virtually while he self-isolates at home.
"Due to stricter entry requirements at the Olympic Games, this means that the crown prince does not have the opportunity to travel to Japan," the Danish royal house said in a statement.
Frederik has frequently appeared in crowds to cheer Danish athletes on during past Olympics. He also carried the torch as the Olympic flame made its way to London in 2012.
Crown Princess Mary and their children Prince Christian, Princess Isabella, Prince Vincent and Princess Josephine don't have to quarantine because they didn't have contact with the person in question.
A few weeks ago, Duchess Kate was forced to self-isolate after close contact with someone who later tested positive for COVID-19. The Duchess of Cambridge was also fully vaccinated. She left quarantine a week later to attend the Wimbledon men's and women's singles final matches.
As mentioned, the Tokyo Olympics officially open on July 23. They were originally due to take place in 2020, but were postponed due to the coronavirus pandemic.
COVID-19 has continued to pose a threat to the Games. Toshiro Muto, the chief of the Tokyo 2020 organizing committee, said on July 20 that he wouldn't rule out cancelling the event altogether if coronavirus cases keep rising in Tokyo. According to Reuters, at least 67 people accredited for the Olympics have tested positive for COVID-19 since July 1.