Vaccine sceptics are attacking Travis Kelce for taking part in a Pfizer advertisement, recycling conspiracy theories about Covid-19 shots as the NFL star is getting attention for his rumoured romance with pop icon Taylor Swift.

As Swift’s fans flooded social media with reactions to her appearance at last Sunday’s Kansas City Chiefs’ win over the Chicago Bears, some of the internet’s most notorious disinformers exploited the buzz, falsely claiming in posts naming the tight end that vaccines cause widespread heart problems or kill people. Some barbs hit Swift as well.

“What will break Kelce’s heart first? The Covid shot or Taylor Swift?” Charlie Kirk, founder of conservative organisation Turning Point USA, wrote in one of several posts AFP saw echoing a conspiracy theory about the jabs triggering cardiac arrests in athletes.

Another post from a top promoter of the QAnon conspiracy theory on X, formerly Twitter, went a step further: “He wants to make sure you get your DOUBLE kill shot.”

The attempts to hijack the narrative surrounding the celebrity duo underscore how promoters of vaccine misinformation readily take advantage of the day’s headlines.

Coronavirus: US FDA approves updated Covid-19 vaccines

Similar allegations casting vaccines as deadly dominated X and other sites after Buffalo Bills safety Damar Hamlin collapsed in a February incident resulting from a blow to his chest.

“Anti-scientific voices often abuse trending stories,” said Yotam Ophir, an expert on health misinformation at the University of Buffalo. “Celebrities in this case simply serve as an easy hook for pulling large amounts of people into the conspiracy world.”

“The Kelce-Swift photos are all over the internet,” Ophir said. “And people know that anything about the couple, true or false, will attract attention.”

Kelce has long advocated for Covid-19 vaccination, which have proven safe, appearing in a 2021 promotion for the shots with US pharmacy chain Walgreens.

His paid partnership with Pfizer shows him flashing a pair of bandages on his shoulder while encouraging viewers to get the latest Covid-19 booster and a flu shot at the same time.

The two-time Super Bowl champion disabled comments under his September Instagram post sharing the ad. But angry users lit up other posts on his page with debunked claims about vaccine safety and personal attacks saying he “sold his soul” for “promoting killer injections.”

The backlash also spilled onto other platforms, from X and Reddit to fringe internet forums, where some users speculated that he struck a “deal” to endorse the vaccines in exchange for Swift’s attention.

Stew Peters, the far-right creator of a conspiracy-laden film about the shots, said on his show that Kelce and Swift are “responsible for murder,” including of children.

A guest replied that “people deserve to be publicly prosecuted and hung.”

There is consensus that annual Covid-19 jabs will benefit the most vulnerable.

The rare risk of myocarditis, or inflammation of the heart, in younger people has seen some countries narrow their booster campaigns, but the United States recommends everyone six months and older receive the updated shot.

More Americans turn anti-vax as Covid jab conspiracies spread

A recent Kaiser Family Foundation poll found that fewer than 50 per cent of eligible adults expect to get the latest Covid-19 booster, and most parents do not plan to get it for their children.

Experts worry anti-vaccine harassment campaigns could make public figures – and medical professionals – less likely to forcefully back the new shots.

“This type of backlash not only can inhibit celebrities from encouraging vaccination, but also can discourage scientists,” said Heidi Larson, director of The Vaccine Confidence Project.

“In both cases, the result could be shameful self-censorship,” Buffalo’s Ophir added. “Yet another win for falsehood over truth in the digital environment.”