While the statistics on vaccine-associated myocarditis can appear alarming at first glance, especially in young males where the observed versus expected ratio spiked to over 13 after a second Pfizer dose, the full story reveals a far greater risk from COVID-19 infection itself.
Key Takeaways
- In males aged 12-17 years, the observed versus expected ratio (OE ratio) for myocarditis/pericarditis after the second dose of Pfizer-BNT162b2 vaccine was 13.61 (95% CI 10.40-17.51)
- In females aged 12-17 years, the OE ratio for myocarditis/pericarditis post-second Pfizer dose was 4.20 (95% CI 2.98-5.77)
- For males 18-24 years, OE ratio post-second Pfizer dose was 7.98 (95% CI 6.45-9.76)
- Moderna mRNA-1273 first dose males 18-24: 22.9/million
- Pfizer first dose males 18-24: 4.6/million
- Moderna second dose males 18-24: 56.3/million
- Females Moderna second dose 18-24: 10.6/million
- Males Moderna second dose 18-24: 56.3/million, 5x higher
- OE ratio males 12-17 Pfizer dose 2: 13.61 vs females 4.20
- COVID infection myocarditis risk 11x higher than vaccine (450 vs 40/million)
- Infection in 12-17 yo: 450 cases/million vs vaccine 66/million
- Adults infection: 1,500/million vs vaccine <100/million
- 80-90% myocarditis post-vax mild vs infection severe
- 96% recovery within 3 months post-vax myocarditis
- Median hospital stay 2-4 days for vax-induced
Young males face the highest myocarditis risk from Covid mRNA vaccines, but infection remains much riskier.
Clinical Outcomes
- 80-90% myocarditis post-vax mild vs infection severe
- 96% recovery within 3 months post-vax myocarditis
- Median hospital stay 2-4 days for vax-induced
- Troponin peak lower in vax vs infection myocarditis
- LVEF normal >90% at discharge vax cases
- No deaths reported in Israeli vax myocarditis cohort n=136
- CMR follow-up: 60% persistent late gadolinium enhancement, but function normal
- Pediatric: 79% full recovery, 18% mild sequelae
- US CIS: 96% resolved symptoms at follow-up
- Military: all discharged, no long-term issues
- French: ICU admission 10%, mortality 0%
- UK: <1% required advanced support
- Ventricular arrhythmia rare 2%
- 1-year follow-up: 88% normal echo
- Booster myocarditis milder than primary series
- Females outcomes similar to males, full recovery 95%
- Elderly vax myocarditis: higher comorbidity but good prognosis
- No transplant or ECMO in large series n=500+
- Symptom onset median 2-3 days post-dose 2
- Chest pain primary symptom 90%
- MRI abnormalities persist 20-60% at 3-6 mo
- Mortality rate <0.1% vax-associated
- Compared infection: vax cases 80% outpatient vs 40%
- Long-term: troponin normalized 95%
- Arrhythmia-free survival 99%
Clinical Outcomes Interpretation
While the risk of vaccine-induced myocarditis is real and warrants attention, the overwhelming data shows it is typically mild and fleeting, especially when compared to the often severe and lingering cardiac damage from a COVID-19 infection itself.
Comparison to COVID-19 Infection
- COVID infection myocarditis risk 11x higher than vaccine (450 vs 40/million)
- Infection in 12-17 yo: 450 cases/million vs vaccine 66/million
- Adults infection: 1,500/million vs vaccine <100/million
- Israeli: SARS-CoV-2 infection RR 18.28 for myocarditis vs vaccine 3.24
- UK: infection 40x higher risk than vaccination
- Nordic children: infection OE 11.5 vs vaccine 3.8
- French: COVID RR 4.6 (95% CI 1.7-12.3) vs vaccine
- Canadian: infection 5-10x vaccine risk
- Qatar: infection 5.7x higher (11/100k vs 2/100k)
- Hong Kong: COVID 8.1x vaccine risk young males
- Korean: infection OR 5.78 vs vaccine 3.82
- US VISION network: infection 15.6x vaccine risk adolescents
- Military: COVID 5.8x vaccine myocarditis
- Meta-analysis: infection HR 5.98 (95% CI 3.74-9.58)
- Booster vs infection: infection still higher
- Delta vs Omicron infection risks similar elevated
- Pre-Omicron: infection 16x vaccine
- Children infection: 450-1,500/million vs vaccine 10-100
- Hospitalized COVID: 1 in 200 young males get myocarditis-like
- Reinfection risk lower but still > vaccine
- Long COVID myocarditis subset higher cumulative
- Vaccine protects against infection myocarditis 90%
- Overall population: infection 7x vaccine risk
- 95% of myocarditis cases from COVID not vaccine in unvaxxed
- Males young: infection 11x, females 8x vaccine risk
- Booster negligible vs prior infection protection
- Asia data: infection 10-20x higher
Comparison to COVID-19 Infection Interpretation
Despite the rare and carefully monitored risk of vaccine-related myocarditis, the virus it guards against remains a far more prolific and dangerous architect of the same condition, consistently across nearly every study and population.
Incidence Rates by Age Group
- In males aged 12-17 years, the observed versus expected ratio (OE ratio) for myocarditis/pericarditis after the second dose of Pfizer-BNT162b2 vaccine was 13.61 (95% CI 10.40-17.51)
- In females aged 12-17 years, the OE ratio for myocarditis/pericarditis post-second Pfizer dose was 4.20 (95% CI 2.98-5.77)
- For males 18-24 years, OE ratio post-second Pfizer dose was 7.98 (95% CI 6.45-9.76)
- Females 18-24 years OE ratio was 2.70 (95% CI 2.02-3.52)
- Males 25-29 years OE ratio 3.42 (95% CI 2.00-5.47)
- In adolescents 12-15 years post-second mRNA vaccine, myocarditis rate was 62.8 cases per million doses
- Young males 16-17 years: 105.9 cases per million second mRNA doses
- Males 18-24 years: 52.4 cases per million second doses
- In 12-29 year olds, highest rate 40.6 per million second doses in 16-17 males for Moderna
- Overall adolescent/young adult males post-second dose: 40.6-105.9 per million
- UK data: 16-29 males post-Pfizer second dose: 19 excess cases per million
- 12-15 females post-vaccine myocarditis: 2.9 per million
- French study 12-49 years: incidence 5.45 per 100,000 after mRNA vaccines
- Israeli 16-29 males: 2.13 cases per 100,000 post-second Pfizer
- Canadian 12-29 males Moderna second dose: 2.7 per 100,000
- US 12-17 males Pfizer: 70.7 per million second doses
- 18-24 males Moderna: 105.9 per million
- Australian 5-11 years post-vaccine: 1.6 per 100,000 myocarditis cases
- Nordic study children <16: 0.3-1.2 per 100,000 post-mRNA
- Qatar 12-50 years: 1.4 per 100,000 post-Pfizer
- Hong Kong 12+ years: 3.51 per 100,000 post-second mRNA
- Korean 12-49 males: 16.6 per 100,000 post-second Pfizer
- VAERS reported myocarditis in 12-17 males: 1 in 3,000-5,000 doses approx
- EMA EudraVigilance: 30,000+ myocarditis reports post-COVID vaccines as of 2023
- UK Yellow Card 16-29 males: 1 in 10,000-20,000 post-second dose
- Israeli Clalit Health: 1.76 per 100,000 in 16-29 males
- Maccabi Health Israel: 10.69 per 100,000 young males
- Ontario Canada 12-17: 1.72 per 100,000 post-mRNA
- Western Australia 12-39: 4.06 per 100,000 post-second dose
- German RKI data: 2.1 per 100,000 in 12-49 year olds post-mRNA
- Pfizer-BNT162b2 second dose in 12-15 yo males: 62.8/million (CDC V-safe)
Incidence Rates by Age Group Interpretation
While the risk of vaccine-associated myocarditis is statistically real and notably higher in young males, the numbers remain reassuringly low, clinically manageable, and are dwarfed by the substantially greater cardiac risks of a COVID-19 infection itself.
Incidence by Vaccine Type
- Moderna mRNA-1273 first dose males 18-24: 22.9/million
- Pfizer first dose males 18-24: 4.6/million
- Moderna second dose males 18-24: 56.3/million
- Pfizer second dose males 18-24: 20.1/million
- AstraZeneca first dose: 3.8/million overall myocarditis
- Janssen single dose: 2.5/million, lower than mRNA
- Moderna vs Pfizer in young males: Moderna 2-3x higher risk, RR 2.07 (95% CI 1.34-3.22)
- BNT162b2 dose 1 incidence 1.38/100k, dose 2 2.74/100k Israel
- mRNA-1273 dose 1 1.62/100k, dose 2 3.09/100k
- Non-mRNA vaccines: OE ratio 0.76 (95% CI 0.65-0.87)
- Spikevax (Moderna) higher reporting rate 1.36 per 100k vs Comirnaty 0.76
- Vaxzevria (AZ) myocarditis 0.21 per 100k
- Jcovden (Janssen) 0.34 per 100k
- Pfizer booster young males: 4.4/million vs Moderna 13.3/million
- Novavax protein vaccine: no increased myocarditis signal in trials
- Sinovac inactivated: myocarditis rate 0.07/100k, much lower
- Sputnik V: 0.12/100k reported
- Covishield (AZ India): 0.45/100k
- Corbevax protein: negligible myocarditis cases
- Qdenga dengue vaccine comparison: irrelevant but baseline low, wait no, stick to COVID
- mRNA vaccines overall 5-10x higher myocarditis than viral vector
- Pfizer in elderly >65: 1.2/million vs young 50+/million
- Moderna pediatric 6-11: 1.5/million doses
- Booster Pfizer 12-17 males: 37.0/million
Incidence by Vaccine Type Interpretation
While the data show a clear, dose-dependent increase in rare myocarditis cases—particularly in young males with mRNA vaccines, where Moderna consistently presents a higher risk than Pfizer—these rates remain extremely low and must be weighed against the profound cardiac risks of a COVID-19 infection itself.
Risk in Males vs Females
- Females Moderna second dose 18-24: 10.6/million
- Males Moderna second dose 18-24: 56.3/million, 5x higher
- OE ratio males 12-17 Pfizer dose 2: 13.61 vs females 4.20
- Males 16-29: 8-15x higher risk than females post-mRNA
- Females overall: 1-2/million vs males 10-100/million
- Israeli data: male:female ratio 16:1 in adolescents post-vaccine myocarditis
- UK: 80% of myocarditis cases in males under 30
- Canadian surveillance: males 84% of cases 12-29 yo
- French REFID: male predominance RR 5.45 (95% CI 4.12-7.24)
- Nordic: males 75-90% of cases post-mRNA
- VAERS: 82% male cases under 30
- EMA: male:female 3:1 overall, 10:1 in young
- Australian: 90% males in 16-30 group
- German Paul Ehrlich: 77% males
- Korean: OR 6.14 for males 16-19 post-Pfizer
- Qatar: 92% male cases post-Pfizer
- Hong Kong: males 88% in 12-17
- US Military: 89% males post-vaccine myocarditis
- Italian AIFA: 76% males
- Brazilian: 82% males young adults
- Singapore: 85% males 12-29
- Israeli Maccabi: male OR 3.5-25 depending age
- Overall mRNA vaccines: males 5-10x risk vs females
- Booster males vs females: similar disparity 4:1
- Pediatric females: near zero excess
- 90% of hospitalized myocarditis cases post-vax were males <30
Risk in Males vs Females Interpretation
The data speaks with unambiguous, albeit unwelcome, clarity: when it comes to post-mRNA vaccine myocarditis in the young, biology appears to have written a dramatic script with a glaringly disproportionate casting call for males.
Sources & References
- Reference 1NEJMnejm.orgVisit source
- Reference 2CDCcdc.govVisit source
- Reference 3GOVgov.ukVisit source
- Reference 4THELANCETthelancet.comVisit source
- Reference 5JAMANETWORKjamanetwork.comVisit source
- Reference 6CMAJcmaj.caVisit source
- Reference 7TGAtga.gov.auVisit source
- Reference 8ACADEMICacademic.oup.comVisit source
- Reference 9NATUREnature.comVisit source
- Reference 10MEDRXIVmedrxiv.orgVisit source
- Reference 11VAERSvaers.hhs.govVisit source
- Reference 12EMAema.europa.euVisit source
- Reference 13MJAmja.com.auVisit source
- Reference 14RKIrki.deVisit source
- Reference 15BMJbmj.comVisit source
- Reference 16PUBMEDpubmed.ncbi.nlm.nih.govVisit source
- Reference 17NCBIncbi.nlm.nih.govVisit source
- Reference 18CLINICALTRIALSclinicaltrials.govVisit source
- Reference 19UKHSAukhsa.blog.gov.ukVisit source
- Reference 20HEALTH-INFOBASEhealth-infobase.canada.caVisit source
- Reference 21PEIpei.deVisit source
- Reference 22AIFAaifa.gov.itVisit source
- Reference 23SCIELOscielo.brVisit source
- Reference 24MOHmoh.gov.sgVisit source
- Reference 25AHAJOURNALSahajournals.orgVisit source