Australian Open: Authorities cancel Novak Djokovic's visa due to lack of evidence of medical exemption. The world number one, whose vaccination status is unknown, spent the night at Melbourne airport and has been asked to leave the country - FILE - Novak Djokovic (SRB) during his first round match at the 2020 Australian Tennis Open at Melbourne Park in Melbourne, Australia, on January 20, 2020. Photo by Corinne Dubreuil/ABACAPRESS.COM