Day 682: Myopericarditis in Ontario

There's an important preprint out of Ontario about local rates of "myocarditis/pericarditis" after vaccination, stratified by mRNA vaccine. H/T Vinay Prasad, who made a video about the results and their implications for vaccine policy. The conclusion:

Results: There were 19,740,741 doses of mRNA vaccines administered and 297 reports of myocarditis/pericarditis meeting our inclusion criteria. Among these, 69.7% occurred following the second dose of COVID-19 mRNA vaccine and 76.8% occurred in males. The median age of individuals with a reported event was 24 years. The highest reporting rate of myocarditis/pericarditis was observed in males aged 18-24 years following mRNA-1273 [Moderna] as the second dose; the rate in this age group was 5.1 (95% CI 1.9-15.5) times higher than the rate following BNT162b2 [Pfizer] as the second dose. Overall reporting rates were higher when the inter-dose interval was shorter (i.e., ≤30 days) for both vaccine products. Among individuals who received mRNA-1273 [Moderna] for the second dose, rates were higher for those who had a heterologous as opposed to homologous vaccine schedule.

Conclusions and Relevance: Our results suggest that vaccine product, inter-dose interval and vaccine schedule combinations may play a role in the risk of myocarditis/pericarditis, in addition to age and sex. Certain programmatic strategies could reduce the risk of myocarditis/pericarditis following mRNA vaccines.

Dr. Prasad goes into some detail about the various rates of myocarditis, some of which were quite high, and the "programmatic strategies" (avoiding Moderna and spacing shots more widely) for reducing this side-effect in young males. Nevertheless, PlagueBlog continues to recommend not injecting people who are at negligible risk of dying of COVID with vaccines that pose unprecedented risks of cardiac side effects.