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Aim: Myocarditis is a recognized safety concern following COVID‐19 mRNA vaccination. However, there is limited research quantifying the risk associated with the third dose or comparing the risk between the three doses. The US Vaccine Adverse Event Reporting System (VAERS) is a passive surveillance system that monitors rare adverse events after US‐licensed vaccination. However, studies analyzing VAERS data have often faced criticism for underreporting cases and lacking a control group to assess the increase in baseline risk. Methods: The temporal association between myocarditis onset and COVID‐19 vaccination was studied. To overcome limitations, a novel modified self‐controlled case series method was employed, explicitly modeling the case reporting process in VAERS data. Results: We found an increased risk of myocarditis during the 1‐ to 3‐day period following the second and third doses of both the BNT162b2 vaccine and the mRNA‐1273 vaccine. Following the second dose, the relative incidence (RI) was 4.89 (95% confidence interval (CI), 2.39–10.08) for the BNT162b2 vaccine and 2.86 (95% CI: 1.18–7.03) for the mRNA‐1273 vaccine. Similarly, following the third dose, the RI was 9.04 (95% CI: 2.79–40.99) for the BNT162b2 vaccine and 4.71 (95% CI: 1.42–19.09) for the mRNA‐1273 vaccine. No significant increase in risk was observed during other periods. Notably, our analysis also identified a similar increased risk of myocarditis among individuals aged below 30. Conclusions: These findings raise safety concerns regarding COVID‐19 mRNA vaccines, provide insights into the quantification of myocarditis risk at different postvaccination periods, and offer a novel approach to interpreting passive surveillance system data. [ABSTRACT FROM AUTHOR]

Concerns remain regarding the rare cardiovascular adverse events, myocarditis and pericarditis (myo/pericarditis), particularly in younger individuals following mRNA COVID-19 vaccination. Our study aimed to comprehensively assess potential safety signals related to these cardiac events following the primary and booster doses, with a specific focus on younger populations, including children as young as 6 months of age. Using the Vaccine Adverse Events Reporting System (VAERS), the United States national passive surveillance system, we conducted a retrospective pharmacovigilance study analyzing spontaneous reports of myo/pericarditis. We employed both frequentist and Bayesian methods and conducted subgroup analyses by age, sex, and vaccine dose. We observed a higher reporting rate of myo/pericarditis following the primary vaccine series, particularly in males and mainly after the second dose. However, booster doses demonstrated a lower number of reported cases, with no significant signals detected after the fourth or fifth doses. In children and young adults, we observed notable age and sex differences in the reporting of myo/pericarditis cases. Males in the 12–17 and 18–24-year-old age groups had the highest number of cases, with significant signals for both males and females after the second dose. We also identified an increased reporting for a spectrum of cardiovascular symptoms such as chest pain and dyspnea, which increased with age, and were reported more frequently than myo/pericarditis. The present study identified signals of myo/pericarditis and related cardiovascular symptoms after mRNA COVID-19 vaccination, especially among children and adolescents. These findings underline the importance for continued vaccine surveillance and the need for further studies to confirm these results and to determine their clinical implications in public health decision-making, especially for younger populations. [ABSTRACT FROM AUTHOR]

An increasing number of myocarditis/pericarditis incidences has been reported after coronavirus disease-19 (COVID-19) vaccination in adolescents and young adults. This study was designed to investigate the incidence rate of—and risk for—myocarditis and pericarditis following COVID-19 vaccination in the United States according to age and vaccine type. This study used the Vaccine Adverse Events Reporting System (VAERS) from 11 December 2020 to 13 August 2021. A population-based data mining approach was performed based on the reporting odds ratio (ROR). Adverse events of myocarditis and pericarditis following COVID-19 vaccination were rare, with an incidence rate of 5.98 (95% CI = 5.73–6.24) cases per million doses administered. The incidence rate was higher in adolescents and after the administration of the second dose of messenger RNA (mRNA) vaccines. Overall, two mRNA vaccines were significantly associated with increased risks for myocarditis/pericarditis (mRNA-1273 (Moderna): ROR = 2.91, 95% CI = 2.21–3.83; BNT162b2 (Pfizer–BioNTech): ROR = 5.37, 95% CI = 4.10–7.04) compared to all other vaccines from VAERS. The viral vector vaccine of Ad26.COV2.S (Janssen) was not associated with signals of myocarditis/pericarditis (ROR = 1.39; 95% CI = 0.99–1.97). This study found increased risks for myocarditis/pericarditis following mRNA COVID-19 vaccines. For patients at high risk for myocarditis/pericarditis or with myocardial injuries, the viral vector vaccine may be an alternative for consideration. [ABSTRACT FROM AUTHOR]