What is the clinical evidence from this study?

Study design: Observational. Population: Myocarditis and/or pericarditis. Intervention: mRNA-1273 vs. BNT162b2. Primary outcome: Myocarditis and/or pericarditis following a second dose in males aged 18-29 years (RR 4.72, 95% CI 3.09-7.39, p=<0.001).

May 25, 2022Open Access

Myocarditis and/or pericarditis risk after mRNA COVID-19 vaccination: A Canadian head to head comparison of BNT162b2 and mRNA-1273 vaccines

Q: What are the key findings of this study?

The risk of myocarditis and/or pericarditis following a second dose of the mRNA-1273 vaccine was 4.72 times higher than after the BNT162b2 vaccine in males aged 18-29 years.

Q: What does this research mean for the field?

The risk of myocarditis and/or pericarditis following a second dose of the mRNA-1273 vaccine is 4.72 times higher than after the BNT162b2 vaccine in males aged 18-29 years. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

Key Result

The risk of myocarditis and/or pericarditis following a second dose of the mRNA-1273 vaccine was 4.72 times higher than after the BNT162b2 vaccine in males aged 18-29 years.

Study Design

Type

Observational

Multicenter

Yes

Structured PICO

Does the mRNA-1273 COVID-19 vaccine increase the risk of myocarditis and/or pericarditis compared to the BNT162b2 vaccine in young adults?

Population

Individuals aged 18-39 years who received mRNA COVID-19 vaccines in Canada, with a specific focus on males aged 18-29 years receiving a second dose.

Intervention

mRNA-1273 (Moderna Spikevax) COVID-19 vaccine

Comparator

BNT162b2 (Pfizer-BioNTech Comirnaty) COVID-19 vaccine

Outcome

Myocarditis and/or pericarditis during the week after vaccinationsafety

The mRNA-1273 COVID-19 vaccine is associated with a significantly higher risk of myocarditis and/or pericarditis compared to the BNT162b2 vaccine in young adults, particularly males aged 18-29 years.

Main Result

Effect estimate: RR 4.72 (95% CI 3.09-7.39)

p-value: p=<0.001

Limitations

Incomplete information on documented prior infections that may have contributed to or caused the presentation
Misclassification of myocarditis and pericarditis can occur
Passive AEFI surveillance tends to suffer from underreporting
A proportion of cases diagnosed in physician offices or not at all may not be captured in background rates
Uncertainty in optimal methodology for calculating background rates during the pandemic due to healthcare avoidance

Abstract

BACKGROUND: Canadian and international data suggest the risk of myocarditis and/or pericarditis is elevated during the week after mRNA COVID-19 vaccination, particularly in younger age groups, in males, and after second doses. OBJECTIVES: This article examines whether there is a product-specific difference in the risk for myocarditis and/or pericarditis between the two mRNA vaccines administered in Canada: BNT162b2 (Pfizer-BioNTech Comirnaty) and mRNA-1273 (Moderna Spikevax). MATERIALS AND METHODS: Reporting rates of myocarditis and/or pericarditis were calculated from reports received by the Canadian Adverse Events Following Immunization Surveillance System from December 2020-March 2022. Excess cases and attributable incidence among individuals aged 18-39 were estimated for each vaccine in comparison with background rates from 2015 to 2019. Head-to-head comparisons used Poisson regression, conditioned on week of vaccine administration, to estimate rate ratios for the week after mRNA-1273 vaccination versus the week after BNT162b2, by age and sex as well as overall. Analyses were restricted to May 30-March 13, 2021, when heightened media awareness was unlikely to have affected reporting rates for the two products differentially. RESULTS: In 18-29 year-old males who received a second dose of mRNA COVID-19 vaccine, attributable risk of myocarditis and/or pericarditis was found to be 5.69 (95% CI: 4.07 - 7.95; p < 0.001) times higher among mRNA-1273 recipients (n = 106) as compared to BNT162b2 recipients (n = 33). In the same group, Poisson regression modelling estimated that the risk of myocarditis and/or pericarditis was 4.72 (p-value = <0.001) times higher after mRNA-1723 compared to BNT162b2 vaccination. CONCLUSIONS: The risk of myocarditis and/or pericarditis is higher after mRNA-1723 vaccination than BNT162b2 vaccination in those aged 18-39 years, especially in males aged 18-29 years, where the risk is several times higher.

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