8 The 76th-ranked Swiss took the biggest upset victory of her career, defeating four-time Grand Slam champion Osaka by 3-6, 6-3, 6-3 at the final major US Open tuneup tournament
Medvedev, who was seeded second behind top-ranked Novak Djokovic at the ATP Masters 1000 event on clay, has been put in isolation and is being monitored, the men's tennis governing body said in a statement.
"My focus is now on recovery and I look forward to getting back out on Tour as soon and as safely as possible."
Both the ATP and the women's WTA said it recommended players accept vaccine shots when available after some at the Miami Open this week expressed a reluctance to get vaccinated.
Professional tennis, which requires players to jet around the world, was shut down for five months last year as countries locked down borders to stem the spread of the virus.
The former world No.1 is reportedly in good health and isolating at his residence in Surrey.
The three-time Major champion had been due to fly down to Australia this week to complete a two-week quarantine Down Under before the first Grand Slam of the season on February 8.
The ATP tournament scheduled to take place in Adelaide has been moved to Melbourne to be played in the week commencing Jan. 31 alongisde another men's tournament in the city.