Tennis fans 12 years or older will be required to show proof of a COVID-19 vaccine in order to attend the US Open.
Just three days before the main draw is set to begin, the New York City mayor's office on Friday mandated proof of vaccine to enter Arthur Ashe Stadium, the main venue for primetime matches.
The United States Tennis Association then elected to extend the vaccine requirement to all attendees 12 years old or older at the Billie Jean King National Tennis Centre, regardless of which facilities ticketholders plan to access.
"Any US Open attendee with tickets to Arthur Ashe Stadium, Louis Armstrong Stadium, the Grandstand, or the grounds of the US Open, will be required to provide proof of at least one dose of a COVID-19 vaccine," the USTA said in a statement.
The USTA confirmed the mandate does not apply to athletes competing in the tournament, some of whom have previously expressed reluctance to receive the shot.
World No.3 Stefanos Tsitsipas said earlier this month he would only get the COVID-19 vaccine if it became mandatory to compete in tennis.
The announcement marked an abrupt change for the US Open, the crown jewel of the American tennis calendar and the year's final major, which previously said it would rely on unvaccinated fans to wear masks.
The tournament was held without fans in 2020.