Prevalence of mRNA/pericarditis after mRNA COVID-19 vaccination in children and young adults in the United States

According to the Annals of Internal Medicine study, in this population-based surveillance, the authors found that in people aged 5 to 39 years, the chance of developing myocarditis/pericarditis 0 to 7 days after mRNA inoculation was about one in 200,000, about one in 30,000 after the second dose of the primary series, and about one in 50,000 after the first fortification
.
However, incidence varies significantly by age and sex, and the number of cases in men is disproportionate, especially among adolescents after the 2nd dose and the
first booster.

The authors observed that the incidence after the first synergist was generally higher than after the first dose, which is consistent
with the Israeli report.
However, contrary to this earlier report, they did not consistently observe that in primary vaccine series, the incidence after the first dose of fortified agent was lower than after the second dose
.
The incidence of myocarditis/pericarditis observed in the VSD population was higher than in the population reported to the US Vaccine Adverse Event Reporting System (VAERS), especially after the first intensification, but the pattern was similar
in the gender and age subgroups.
The rate reported by VAERS may be lower because the passive nature of VAERS reports differs from the nature of VSD using active surveillance to identify cases
.
Both VSD and VAERS found that the incidence within 0-7 days of vaccination was higher than the pre-pandemic background rate noted by Auster and colleagues; However, pre-pandemic incidence may not be directly comparable to post-vaccination incidence, as underdiagnosis of myocarditis/pericarditis in this age group is more likely to occur before the pandemic than after
vaccination when the level of surveillance is higher.