Heute reports that Thiem - currently injured - will not be granted an exemption to visit the home event as a spectator.

The unvaccinated former US Open champion has said he is waiting to receive a Novavax vaccine as it uses an "inactivated" protein-based formula, but the jab has not yet been approved.

"I can only ask Dominic Thiem to get vaccinated," said Wolfgang Mückstein, a practicing doctor and Austrian Minister of Social Affairs, Health, Care and Consumer Protection, per Agence France-Presse.

"The inactivated vaccines may not be available until 2022, and there is no indication that they have any advantages over current vaccines."

Mückstein also warned of the risk of long COVID for the 28-year-old, who despite being an athlete could still suffer the ill effects of the virus.

Thiem is one of many tennis players who have so far refused to receive inoculations against coronavirus, with it estimated that roughly a third of players on the Association of Tennis Professionals and Women's Tennis Association (WTA) Tours have not received a first dose.

Several top-10 men's players, including Serbia's 20-time Grand Slam champion Novak Djokovic, current US Open champion Daniil Medvedev from Russia and Greek Stefanos Tsitsipas, have expressed vaccine scepticism or recently said they have not yet been inoculated.

As a result of the low take-up, there is continued uncertainty over whether unvaccinated players will be allowed to play at next year's Australian Open in Melbourne.

The country's Prime Minister, Scott Morrison, said that such athletes would receive an exemption from strict travel restrictions to allow them into Australia.

However, Victoria Premier Daniel Andrews refuted Morrison's claim and insisted the state "will not be applying for an exemption for any unvaccinated player", leaving them unable even to fly to Victoria and complete 14 days of quarantine before the tournament.

This has cast doubts in particular over whether world number one Djokovic will be able to compete.

An email from the WTA Player Council leaked earlier this week claimed that unvaccinated players would be subjected to two weeks of "hard quarantine" and those with two doses would have "complete freedom of movement" during their time in Melbourne.