Question explored with the scientific record
Does Covid cause myocarditis
The short version: COVID infection clearly causes myocarditis at rates that dwarf the vaccine's risk, but the absolute risk for most people is low either way.
The evidence is consistent across multiple studies and countries. A large English study of 38.6 million people found 40 extra myocarditis events per million in the 28 days after a positive SARS-CoV-2 test, compared with 1-10 per million after mRNA vaccination [9]. A meta-analysis reported the relative risk of myocarditis was seven times higher in infected patients than in vaccinated groups [3]. One cohort study found the risk was 16 times higher in COVID patients than in uninfected people [3]. Autopsy data shows myocarditis in about 7% of COVID deaths, though the true prevalence in all infections is likely under 2% [4].
The mechanism is biologically plausible. SARS-CoV-2 can directly infect heart cells, trigger widespread inflammation, and cause microclots that damage heart tissue [1, 13]. The infection-associated myocarditis is also more severe: it more frequently leads to ventricular dysfunction, arrhythmias, and death [3]. In contrast, vaccine-associated myocarditis is typically mild, resolves with anti-inflammatory drugs, and rarely causes death [3, 9].
The key caveat is that most of this evidence comes from observational studies, not randomized trials. The infection numbers also include hospitalized patients who are sicker than the average infected person, which may inflate the risk. But the pattern is consistent: infection carries a higher risk of myocarditis than vaccination, and the infection-related cases are more dangerous.
| Group | Extra myocarditis events per million | Severity |
|---|---|---|
| SARS-CoV-2 infection | 40 [9] | Ventricular dysfunction, arrhythmias, death [3] |
| Pfizer first dose | 1 [9] | Mild, resolves with NSAIDs [3] |
| Moderna first dose | 6 [9] | Mild, resolves with NSAIDs [3] |
| Moderna second dose | 10 [9] | Mild, resolves with NSAIDs [3] |
My call: COVID infection causes myocarditis at a higher rate and with greater severity than mRNA vaccination. Confidence: moderate. The evidence is consistent but observational, and the absolute risk for a healthy young person from either source is low.
Sources examined 13
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Myocarditis after COVID-19 mRNA vaccination: clinical observations and potential mechanisms
This study examines the incidence and implications of acute myocarditis associated with COVID-19 mRNA vaccination compared to myocarditis resulting from COVID-19 infection, highlighting the rarity of vaccine-related myocarditis and the greater risks associated with COVID-19 itse…
DOI: 10.1038/s41569-021-00662-w -
Disentangling a Thorny Issue: Myocarditis and Pericarditis Post COVID-19 and Following mRNA COVID-19 Vaccines
This pharmacovigilance study analyzes the incidence of myocarditis and pericarditis reported in the Vaccine Adverse Events Reporting System (VAERS) following mRNA COVID-19 vaccinations, revealing a higher incidence in young males after the second dose, but a lower risk compared …
DOI: 10.3390/ph15050525 -
Myocarditis after COVID-19: Comparing risks from vaccination and infection
A meta-analysis and FDA reports show COVID-19 infection carries a higher risk of myocarditis and more severe outcomes than mRNA vaccination, so vaccine benefits outweigh risks.
DOI: 10.47391/jpma.32162 -
COVID-19 and Myocarditis: Review of Clinical Presentations, Pathogenesis and Management
A comprehensive review of how COVID-19, MIS, post-acute COVID-19 syndrome, and vaccination relate to myocarditis, summarizing clinical presentations, proposed pathogenesis, diagnostic approaches, and current management with discussion of limitations and gaps for future research.
DOI: 10.17925/hi.2022.16.1.20 -
Commentary: raised c-troponin levels as a sign of myocardial injury after COVID-19 vaccination in healthy individuals are worrying
This commentary critiques the claim that myocardial injury from COVID-19 infection is more prevalent than that from mRNA vaccination, arguing that empirical evidence suggests the opposite, particularly when considering the broader population affected by vaccination.
DOI: 10.1186/s43044-024-00441-1 -
Changing Epidemiology of Myocarditis in Australia: A Population-Based Cohort Study
This population-based cohort study investigates the changing epidemiology of myocarditis in New South Wales, Australia, revealing a tripling incidence over 20 years, with significant associations to COVID-19 and varying patient demographics.
DOI: 10.3390/jcm13237111 -
Wuhan 3 years after the outbreak of the pandemic—cardiological insights and perspectives
This study reviews the incidence, diagnosis, and management of COVID-19-associated myocarditis in Wuhan, highlighting the significant impact of the Omicron variant on cardiac health and the importance of early identification and treatment.
DOI: 10.1007/s00059-023-05176-4 -
Clinically Suspected Myocarditis in the Course of Severe Acute Respiratory Syndrome Novel Coronavirus-2 Infection: Fact or Fiction?
A comprehensive review synthesizing current data on clinically suspected myocarditis in COVID-19, evaluating ESC criteria versus biopsy/autopsy findings, and concluding that SARS-CoV-2–induced viral myocarditis is not yet proven and remains uncommon.
DOI: 10.1016/j.cardfail.2020.11.002 -
Acute myocarditis caused by COVID-19 disease and following COVID-19 vaccination
This narrative review summarizes evidence that COVID-19 and mRNA COVID-19 vaccination can cause rare myocarditis, most common in younger males after second dose, with favourable short-term course and benefit-risk favouring vaccination.
DOI: 10.1136/openhrt-2021-001957 -
Post-COVID-19 Syndrome vs. Consequences of Vaccination with Special Reference to Cardiovascular Conditions
This paper argues that post-COVID-19 syndrome and COVID-19 vaccination side effects overlap in cardiovascular manifestations through shared spike protein mechanisms, and calls for healthcare vigilance and further research on long-term vaccine risks.
DOI: 10.52768/cardiology/1002 -
Incidence, risk factors, natural history, and hypothesised mechanisms of myocarditis and pericarditis following covid-19 vaccination: living evidence syntheses and review
This living systematic review found that myocarditis after mRNA COVID-19 vaccination occurs most frequently in male adolescents and young adults, with moderate-certainty evidence that Moderna is associated with higher incidence than Pfizer in 18-29 year olds and low-certainty ev…
DOI: 10.1136/bmj-2021-069445 -
Post Covid-19 Myocarditis: When to suspect post-Covid-19 cardiomyopathy and the importance of earlydiagnosis
Adult survivors of COVID-19 may develop myocarditis or pericarditis as post-acute sequelae, with large cohort data suggesting increased risk of adverse cardiovascular outcomes and highlighting the need for early diagnosis and follow-up.
DOI: 10.59471/ijhsc2023145 -
Potential Effects of Coronaviruses on the Cardiovascular System
A concise review of how coronaviruses, particularly SARS-CoV-2, can affect the cardiovascular system, summarizing mechanisms, clinical cardiovascular manifestations (injury, myocarditis, arrhythmias), mortality risk factors, and early guidance on management and potential therapi…
DOI: 10.1001/jamacardio.2020.1286