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mRNA COVID-19 vaccines are associated with a small increase in myocarditis
Clinical Question
Is myocarditis more likely to occur in people who receive an mRNA SARS-CoV-2 (COVID-19) vaccine?
Bottom line
Vaccination with either of the 2 mRNA vaccines — Moderna and Pfizer — is associated with a small increase in the likelihood of developing myocarditis or pericarditis over the subsequent year. The numbers, though, are really, really low (a total of 269 in almost 5 million people), and death rates were less than half among vaccinated people as compared with unvaccinated people. 1b
Reference
Study design: Cohort (prospective)
Funding: Foundation
Setting: Population-based
Synopsis
This study, conducted in Denmark, followed everyone in the Danish Civil Registration System who was 12 years or older (N = 4,931,775) who received at least one dose of a vaccine and did not have a positive COVID-19 test result over the year of data collection. Almost all people in Denmark received the mRNA vaccines BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna). The authors identified all patients admitted to hospital with a diagnosis code of myocarditis or pericarditis who also had increased troponin levels (to focus on patients with biochemically verifiable heart damage). Almost all patients (96%) were available for follow-up. Over the year, 269 people developed myocarditis or myopericarditis. Most (73%) were male and 40% were between the ages of 12 and 39 years. The Moderna vaccine was associated with an increase in myocarditis, especially in the 12- to 39-year-old group. The Pfizer vaccine was associated with an increase in myocarditis in women. Although statistically significant, the rate of carditis was low: Even in the younger age group, the rate was 1.6 (Pfizer) to 5.7 (Moderna) per 100,000 individuals. Both vaccines were associated with a pronounced decrease in the likelihood of cardiac arrest or death as compared with no vaccination (hazard ratio 0.41 or 0.51).
Reviewer
Allen F. Shaughnessy, PharmD, MMedEd
Professor of Family Medicine
Tufts University
Boston, MA
Comments
mRNA vaccines are associated with increased rates of myocarditis
Confirms most of what we already know. This does not alter my endorsement of vaccination against COVID. These rates are extremely low.
mRNA causes increased rates of myocarditis
confirms extremely low rates
mRNA vaccines are associated with increased rates of myocarditis
I am quite curious about the symptoms that these patients presented with.
JG Baribeau - retired GP
ETHICS unclear - what is a "small number of deaths", when co
ETHICS unclear - what is a "small number of deaths", when considering any one patient . . .. ?
It would have been more…
It would have been more helpful to get the hazard ratio for death/cardiac arrest in the 12- to 39-year-old age group to help us better discuss risks with vaccine-hesitant persons in that age group.