Alami: Did Alami et al. (BMJ) show that vaccinated individuals were twice as likely to develop myocarditis/pericarditis in the absence of COVID infection relative to unvaccinated individuals? Yes!

in a 30-day follow-up period, vaccinated individuals (meta-analysis) were twice as likely to develop myo/pericarditis compared to unvaccinated individuals with a rate ratio of 2.05 (95% CI 1.49–2.82).

https://bmjopen.bmj.com/content/13/6/e065687

‘Seven studies met the inclusion criteria, of which six were included in the quantitative synthesis. Our meta-analysis indicates that within 30-day follow-up period, vaccinated individuals were twice as likely to develop myo/pericarditis in the absence of SARS-CoV-2 infection compared to unvaccinated individuals, with a rate ratio of 2.05 (95% CI 1.49–2.82)…a higher risk was detected in those who received mRNA COVID-19 vaccinations compared with unvaccinated individuals in the absence of SARS-CoV-2 infection.’

STRENGTHS AND LIMITATIONS OF THIS STUDY

• Data included in our quantitative synthesis came from several very well-conducted observational studies, and mostly from population-based cohort studies, demonstrating racial and ethnic diversity, with the majority spanning similar time frames.

• All myocarditis and pericarditis cases were adjudicated by at least two methods, minimising the risk of misclassification that can arise from relying on diagnosis codes alone.

• Due to insufficient data, we could not evaluate the possibility of sex differences, or variations in the risk according to the number of doses of mRNA COVID-19 vaccines received.

• Confounding by indication and healthy vaccinee bias may be present in the studies included in our analysis, and it is difficult to determine to what extent these biases may have influenced our risk estimates.