World men's tennis number one Novak Djokovic has had his visa for Australia revoked, after he was granted an exemption from Covid vaccination rules to play in the Australian Open - prompting anger from Australians and a political row.
But what has he actually said about vaccines?
The Serbian star, 34, has not officially disclosed his Covid-19 vaccination status, but he's made his resistance to jabs clear in the past.
In April 2020, well before Covid vaccines were available, Djokovic said he was "opposed to vaccination".
He later clarified his position by adding that he was "no expert" and would keep an "open mind" but wanted to have "an option to choose what's best for my body."
During a Facebook live, he explained that he "wouldn't want to be forced by someone to take a vaccine" to travel or compete in tournaments.
He added that he was "curious about wellbeing and how we can empower our metabolism to be in the best shape to defend against imposters like Covid-19."
In Djokovic's home country, where it's estimated that under half the population is fully vaccinated against Covid, his comments were criticised at the time by government epidemiologist Predrag Kon, who accused the athlete of "creating misconceptions".
The tennis star has a track record when it comes to questionable scientific claims.
In his book Serve to Win, Djokovic described how in 2010 he met with a nutritionist who asked him to hold a piece of bread in his left hand while he pressed down on his right arm. Djokovic claims he was much weaker while holding the bread, and cited this as evidence of gluten intolerance.
And during an Instagram live, he claimed that positive thought could "cleanse" polluted water, adding that "scientists have proven that molecules in water react to our emotions."
According to Dr David Nunan, a senior researcher at the Centre for Evidence Based Medicine at the University of Oxford, "on the balance of probabilities it is highly unlikely that such claims are true - at least not by current conventions of scientific theory and practice."
Earlier in the pandemic, Djokovic's wife repeated a 5G conspiracy theory on Instagram - her post was given a misinformation label by the social network.
While he's been defended by fans and Serbian politicians, the visa dispute has really galvanised anti-vaccination activists, although Djokovic has never explicitly come out in support of their more extreme positions.
In Telegram groups promoting anti-vax theories, he's been portrayed as a hero and an icon of freedom of choice. Twitter users have gathered under hashtags in support of Djokovic and to call for a boycott of the Australian Open.
One influential conspiracy-laced account claimed the star was a "political prisoner" and asked: "If this is what they can do to a multimillionaire superstar, what can they do to you?"