Study of Thai teenagers found one in six experienced heart effects after COVID vaccination

A study of 301 teens in Thailand found mild and temporary heart rhythm changes after a second dose of the Pfizer-BioNTech COVID-19 vaccine among one in six teenagers, not one-third as social media posts claim. The study also saw possible signs of heart inflammation in just seven of those teens with rhythm changes and confirmed myocarditis in only one of the seven.

Social media users are circulating the study of post-vaccination heart effects in Thai teenagers with the claim that a third of participants experienced heart effects, and the suggestion that the results indicate a new danger level for children. These posts are missing context: the study’s authors concluded, “We found the risk of these symptoms to be not as low as reported elsewhere, but in all cases, symptoms were mild with full recovery within 14 days.”

A Twitter post shared more than 11,000 times (here) contains a link to the preprint study by Suyanee Mansanguan of Bhumibol Adulyadej Hospital in Bangkok and colleagues, with the comment, “BREAKING: A new study has found cardiovascular adverse effects in around a third of teens following Pfizer vaccination, and heart inflammation in one in 43, raising fresh concerns about the risks of vaccination for young people. This is beyond concerning.”