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https://www.nature.com/articles/s41591-021-01630-0) > We estimated extra myocarditis events to be between 1 and 10 per million persons in the month following vaccination, which was substantially lower than the 40 extra events per million persons observed following SARS-CoV-2 infection. and they include a brief literature review: > Our findings are consistent with those from a case-control study of 884,828 persons receiving the BNT162b2 vaccine in Israel21. That study observed an association with myocarditis in the 42 days following vaccination (risk ratio of 3.24), but no association with pericarditis or cardiac arrhythmia. Two further studies from Israel add to our observations by providing clinical review to ensure robust case ascertainment22 and reporting investigations and outcomes in individual patients with myocarditis following the BNT162b2 vaccine23. Witberg et al.21,22 observed a small excess in events 3–5 days following the second dose of BNT162b2 vaccine, but most were mild presentations and just one classified as fulminant22. Mevorach et al. observed an incidence ratio of 5.34 for myocarditis in 5,442,696 persons following BNT162b2, although this was attenuated when restricted to the 136 definite and probable cases of myocarditis23. Risk of myocarditis was restricted to males under the age of 40 years and only observed following the second dose. Similarly, two studies from the United States have reported an incident rate ratio of 2.7 for myocarditis in the 10 days following the second dose of both mRNA vaccines24 and an estimated 6.3 and 10.1 extra cases per million doses in the 1- to 21-day period following the first and second dose of both mRNA vaccines, respectively, in those younger than 40 years25. And conclude: > In summary, this population-based study quantifies for the first time the risk of several rare cardiac adverse events associated with three COVID-19 vaccines as well as SARS-CoV-2 infection. Vaccination for SARS-CoV-2 in adults was associated with a small increase in the risk of myocarditis within a week of receiving the first dose of both adenovirus and mRNA vaccines, and after the second dose of both mRNA vaccines. By contrast, SARS-CoV-2 infection was associated with a substantial increase in the risk of hospitalization or death from myocarditis, pericarditis and cardiac arrhythmia. |
It checks for the myocarditis infection from COVID-19, but it doesn't actually control for vaccination status. The people studied either are believed to have been COVID-19 infected, or had been vaccinated, but there was no designated unvaccinated control group.
In which case, you are potentially using "breakthrough cases" of COVID-19 causing Myocarditis to make your point (assuming they would be the same pre- and post- vaccination), rather than a definitive look at people who did not get the vaccine and how they fared. All the study proves is that COVID-19 infections cause increased Myocarditis... in vaccinated people. If you assume that COVID-19 has the same Myocarditis effect in vaccinated and unvaccinated people, it works; but if you accept that maybe the effects of COVID-19 are different in vaccinated people, it could fall apart, which is why the study about how Myocarditis doesn't seem to effect the 160,000+ unvaccinated people studied still has value.