Study did not find millions of children with post-vaccine heart defects

"Bombshell Study Finds 1.7 Million Vaccinated Kids Now Have 'Severe Heart Defects,'" claims a November 19, 2024 headline from The People's Voice, an online outlet which previously spread misinformation fact-checked by AFP.

Screenshots and different versions of the claim spread across Facebook, Instagram and X, with captions purporting that the UK study found millions of children with severe heart conditions after receiving the Covid-19 vaccine.

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Screenshot of an Instagram post taken November 28, 2024

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Screenshot of an X post taken November 28, 2024

The publications follow other false and misleading claims about the shots, which researchers estimate have saved millions of lives (archived here). Claims about Covid-19 jabs sometimes circle around heart conditions -- particularly the inflammation from pericarditis and myocarditis -- as they have been reported as side effects following vaccination.

However, the study referenced in the recent social media posts did not observe millions of children suffering from these conditions (archived here). William Hulme (archived here), a statistical epidemiologist at the Bennett Institute for Applied Data Science and one of the paper's authors, told AFP: "Arguably none of the kids in the study had 'severe heart defects' as reported by us."

The researchers observed 2.7 cases of either myocarditis or pericarditis per 100,000 children after a first vaccine dose and one case per 100,000 after a second dose. These cases were "mild and transient" and Hulme said in a November 27 email they should not be classed as a defect, which "suggests permanent dysfunction or malformation." 

He hypothesized the 1.7 million number in the posts came from the total number of children observed in the study, rather than the small number they saw experiencing the inflammatory conditions.

Mild cases

Other sites and posts skeptical of vaccine safety shared the results of the study, reporting that it had shown that myocarditis and pericarditis only occurred in vaccinated children.

Hulme said that this is "not, strictly speaking, inaccurate" as the two heart conditions were not observed in the study's unvaccinated population. 

However, he said "there are many reasons that our findings might not fully reflect what would have been observed in a randomized trial," including that vaccinated children might be more likely to seek medical care for symptoms consistent with an adverse reaction, even when it is not due to the shot. 

Hulme explained the study was observational and there is a possibility that a randomized trial -- designed differently -- might produce different results (archived here).

According to Johns Hopkins Medicine, myocarditis and pericarditis can also be the result of viral infections or autoimmune diseases (archived here and here).

Hulme also stressed that most cases of myocarditis or pericarditis identified in the research were mild.

"Any hospital stays were no more than two days (if they were admitted to hospital at all)," he said. "Nobody died. So, yes, there was a very small but apparent increase in the occurrence of (mostly mild) myocarditis and pericarditis after vaccination compared with no vaccination."

Vaccine safety reviewed

A 2023 report from the United Kingdom's Medicines and Healthcare products Regulatory Agency mirrors Hulme and his co-authors' observations that post-vaccination cases of myocarditis and pericarditis, while more prevalent in younger people, are typically rare, mild and fast resolving (archived here). 

Observations from the Centers for Disease Control in the United States and Health Canada also record infrequent appearances of myocarditis and pericarditis after vaccination (archived here and here).

All three countries recommend receiving a Covid-19 vaccine since the benefits of preventing serious illness outweigh the risks of the known side effects (archived here and here).

Read more of AFP's reporting on vaccine misinformation here.