COVID-19: epidemiological data on post-vaccination myocarditis and pericarditis


The cardiovascular system can be affected by complications of COVID-19. There are many observations of endocarditis in people affected by this viral infection, but rare cases of endocarditis have also been reported in recent months, following vaccinations against the SARS-CoV-2 virus, with mRNA vaccines.

To shed light on the real impact of these events, a group of North American researchers evaluated the cases of post-vaccination myocarditis or pericarditis in a large cohort of subjects, composing a very precise picture of incidence rates.


Forty North American hospitals participated in the data collection, electronically identifying patients vaccinated for COVID-19, with any type of vaccine.

Cases of patients diagnosed with myocarditis, myopericarditis or pericarditis were then associated with this information.


Over two million individuals who had received at least one dose of the vaccine and with a mean age of 57 years were evaluated.


52.6% received the Pfizer/BioNTech vaccine, 44.1% the Moderna vaccine and 3.1% the Janssen/Johnson & Johnson vaccine.


Twenty individuals developed vaccine-related myocarditis, with a rate corresponding to 1 case per 100,000 vaccinations. Fifteen were males and had a mean age of 36 years.


The onset of myocarditis occurred after a median interval of 3.5 days after vaccination: in 11 cases after administration of the Moderna vaccine and in 9 cases after the Pfizer vaccine.


In most cases, symptoms occurred after administration of the second dose. No deaths were recorded.


At a median of 23.5 days from symptom onset, 13 patients had symptom resolution and 7 were improving.


Thirty-seven subjects developed pericarditis. Its onset was significantly later, appearing at a median interval of 20 days after vaccination.


Pericarditis developed after the first immunization in 15 cases and after the second in 22 cases.


Responsible was the Moderna vaccine in 12 cases, the Pfizer vaccine in 23 cases and the Janssen / Johnson & Johnson vaccine in 2 cases.


Also in the case of pericarditis males were more frequently affected, while the average age was much more advanced than for myocarditis. No deaths were recorded.


At the last available follow-up of the study, recorded at a median interval of 28 days, 19% of patients were asymptomatic and 62% were improving.


In this Research Letter, published in the journal JAMA, the researchers provide consistent data on the incidence of cases of myocarditis or pericarditis following vaccinations with mRNA preparations.

According to the authors, comparing the study data with those provided by the Centers for Disease Control and Prevention, which reports cases of myocarditis with a rate of 4.8 cases per million, it appears that this event is underestimated.


Among the aspects most clearly highlighted by the research, emerge the shorter time interval before the onset of symptoms for myocarditis and the fact that both pericarditis and myocarditis affect much more frequently males.

This post is also available in: Chinese (Simplified)

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