After being stuck in immigration limbo for half a week, the world's tennis number one Novak Djokovic said in a legal challenge on Saturday to being refused entry to Australia that he had been given medical exemption from vaccination against COVID-19 because he had contracted the illness last month.

In a court filing ahead of a hearing on Monday over his visa cancellation Djokovic said he had received the exemption from scandal-plagued tournament organizer, Tennis Australia, with a follow-up letter from the Department of Home Affairs saying he was allowed into the country. By revealing his recently infected status, Djokovic is effectively pushing the debate of natural immunity, which has been extensively maligned by the authorities, vs vaccinations (and their numerous adverse side-effects) to the forefront.

"Mr. Djokovic understood that he was entitled to enter Australia and Victoria and to compete in the Australian Tennis Open," the lawyers wrote. The 35-page filing was released on Saturday.

The Serbian player, hoping to win his 21st Grand Slam at the Australian Open later this month, is on his third day in immigration detention in Melbourne - a case that has caused a sporting, political and diplomatic furore.