How Does Myocarditis Risk with COVID-19 Vaccination Compare to Risk associated with SARS-CoV-2 Infection?
BACKGROUND AND PURPOSE:
- Patone et al. (Nature Medicine, 2021) examined the associations between the first and second dose of AstraZeneca, Pfizer or Moderna vaccines and cardiac adverse events
METHODS:
- Cohort study
- Between December 2020 and August 2021
- English National Immunisation (NIMS) Database of COVID-19 vaccination to national data for mortality, hospital admissions and SARS-CoV-2 infection data
- Population
- Individuals ≥16 years who received ≥1 vaccine dose
- Admitted to the hospital or died from the outcome of interest
- Exposure
- First or second dose of AstraZeneca, Pfizer, or Moderna vaccine
- SARS-CoV-2 infection
- Study design
- The authors calculated risk of primary outcomes at prespecified time periods following exposure
- Primary outcomes
- Myocarditis
- Pericarditis
- Arrythmia
RESULTS:
- Received ≥1 dose of vaccine: 38,615,491
- AstraZeneca (ChAdOx1): 20,615,911 | Pfizer (BNT162b2): 16,993,389 | Moderna (mRNA-1273): 1,006,191
- SARS-CoV-2 infection: 3,028,867
- Myocarditis events: 1615
- Over the 1-to-28-day postexposure period, there was an increased risk of myocarditis associated with
- The first dose of AstraZeneca
- Incidence rate ratio (IRR) 1.29 (95% CI, 1.05 to 1.58)
- The first dose of Pfizer
- IRR 1.31 (95% CI, 1.03 to 1.66)
- The first AND second dose of Moderna
- IRR 2.97 (95% CI, 1.34 to 6.58)
- IRR 9.84 (95% CI, 2.69 to 36.03)
- SARS-CoV-2 infection
- IRR 9.76 (95% CI, 7.51 to 12.69)
- The first dose of AstraZeneca
- Estimate of absolute cases of extra myocarditis events in 1 to 28 days postexposure, per 1 million people
- AstraZeneca first dose: 2 events (95% CI, 0 to 3)
- Pfizer first dose: 1 event (95% CI, 0 to 2)
- Moderna first dose: 6 events (95% CI, 2 to 8)
- Moderna second dose: 10 events (95% CI, 7 to 11)
- SARS-CoV-2 infection: 40 events (95% CI, 38 to 41)
- Other cardiac events
- COVID-19 vaccination was not associated with an increased risk of other cardiac events, except an increased risk of arrhythmia following a second dose of Moderna
- The risks for pericarditis and cardiac arrhythmias were higher following a positive SARS-CoV-2 test
- Subgroup analyses showed an increased risk of myocarditis associated with the mRNA vaccines only in those <40 years
CONCLUSION:
- COVID-19 vaccination is associated with an increased risk of myocarditis
- However, the risk of myocarditis with vaccination is less than the risk associated with SARS-CoV-2 infection itself
- SARS-CoV-2 infection is also associated with increased risk of pericarditis and arrythmias, while vaccination is not
- The authors state
…the mRNA-1273 vaccine roll-out began in April 2021 in the United Kingdom; as a consequence, the number of events in patients who received this vaccine was low
Although the signal associated with myocarditis is strong for this vaccine, care is needed in the interpretation, and it would be useful to replicate our results in similarly large datasets internationally
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