Myocarditis and pericarditis in adolescents after first and second doses of mRNA COVID-19 vaccines

Aims While some concerns about vaccination-related pericarditis and/or myocarditis have been raised, no published data are available on pericarditis and/or myocarditis with mRNA COVID-19 vaccines in the age group of adolescents, particularly 12-15 years. The objective of this study was to determine whether the risk of reporting pericarditis and/or myocarditis with mRNA COVID-19 vaccines varied according to dose of vaccination, age, sex, and type of pericarditis and/or myocarditis in adolescents between 12 and 17 years. Methods and results We performed an observational study reviewing all reports of adolescents vaccinated with mRNA COVID-19 vaccines and recorded in VigiBase(R), the World Health Organization global database of individual case safety reports. We included all reports registered between 1 January 2021 and 14 September 2021. Reporting odds ratios (RORs) with their 95% confidence interval (CI) were calculated to estimate the risk of reporting pericarditis and/or myocarditis. Among 4942 reports with mRNA COVID-19 vaccines in adolescents, we identified 242 pericarditis and/or myocarditis. Compared with the first dose of mRNA COVID-19 vaccines, the second dose was associated with an increased risk of reporting pericarditis and/or myocarditis (ROR 4.95; 95% CI 3.14, 7.89). The risk of reporting pericarditis and/or myocarditis was 10 times higher in boys than in girls and no difference between the two types of vaccines could be demonstrated. Conclusion This investigation including only adolescent data suggests for the first time that the second dose of mRNA COVID-19 vaccines increases the risk of reporting myocarditis/pericarditis compared with the first dose particularly in boys without significant difference between tozinameran and elasomeran.