FILE - Feb. 21, 2021, file photo Serbia&#039;s Novak Djokovic holds the Norman Brookes Challenge Cup after defeating Russia&#039;s Daniil Medvedev in the men&#039;s singles final at the Australian Open tennis championship in Melbourne, Australia. Players who haven&#039;t received a COVID-19 vaccination are unlikely to get a visa to enter the country for the Australian Open next January, according to the political leader of the state which hosts the season-opening major. (AP Photo/Hamish Blair, File)