Post-vaccination myocarditis, a form of heart inflammation, was identified in a subset of people who died “unexpectedly” at home within 20 days of receiving a COVID-19 vaccine. Researchers analyzed autopsies that had been performed on the people and conducted additional research, including studying tissue samples.
Researchers started with a group of 35, but excluded 10 from further analysis because other causes of death were identified. Of the remaining 25, researchers identified evidence of myocarditis in five.
All of the five people received a Moderna or Pfizer vaccine within seven days of their death, with a mean of 2.5 days. The median age was 58 years. None of the people had COVID-19 infection prior to being vaccinated and nasal swabs returned negative.
Autopsy findings combined with the lack of evidence of other causes of death and how the vaccination happened shortly before the deaths enabled researchers to say that for three of the cases, vaccination was the “likely cause” of the myocarditis and that the cardiac condition “was the cause of sudden death.”
In one of the other cases, myocarditis was believed to be the cause of death but researchers detected a herpes virus, an alternative explanation for the incidence of heart inflammation. The remaining case did not include an alternative explanation for the myocarditis but the researchers said the impact of the inflammation was “discrete and mainly observed in the pericardial fat.” They classified the two cases as possibly caused by vaccination.
“In general, a causal link between myocarditis and anti-SARS-CoV-2 vaccination is supported by several considerations,” the researchers said, including the “close temporal relation to vaccination”; the “absence of any other significant pre-existing heart disease”; and the negative testing for any “myocarditis-causing infectious agents.”
Limitations included the small cohort size.
The study (pdf) was published by Clinical Research in Cardiology on Nov. 27. The researchers all work for Heidelberg University Hospital. They were funded by German authorities.
Moderna and Pfizer did not respond to requests for comment.