Temporal relationship of myocarditis and pericarditis following COVID-19 vaccination: A pragmatic approach

Complications following COVID-19 vaccination, particularly with mRNA vaccines, rarely include myocarditis and pericarditis. This work principally aimed at defining a realistic temporal relationship between vaccination and myocarditis/pericarditis development.

All relevant cases reported from week 52/2020 through week 41/2021 in the VAERS database were retrieved and analyzed for licensed vaccines. These included BNT162b2, mRNA-1273, and AD26.COV2·S. Incidence rates were calculated using the corresponding administered vaccine doses as denominators. Additionally, analyzed parameters included demographics, dose series, hospitalization length and outcome.

Overall, 2016 myocarditis and 1380 pericarditis cases, (4.96/10⁶ and 3.40/10⁶ administered vaccine doses, respectively), were recorded. Most myocarditis cases occurred following BNT162b2 (5.60/10⁶ doses) in males <30 years. Pericarditis affected predominantly males <40, both sexes >40 years, and was most common post AD26.COV2·S (4.78/10⁶ doses). Hospitalization was required for 40.3% and 27.2% of myocarditis and pericarditis cases, respectively. A bimodal pattern was found for both myocarditis and pericarditis, with two peaks that coincided temporally, but were reversed in intensity. The first peak was recorded 1-3 days post-vaccination and was more pronounced in myocarditis, while the second was recorded 15-30 days post-vaccination and was more intense in pericarditis.

Myocarditis/pericarditis after COVID-19 vaccination is rare and depicts a bimodal pattern.