Systematic review of cardiac adverse effects in children and young people under 18 years of age after SARS-CoV-2 vaccination

Background Reports of myocarditis and pericarditis following vaccination with mRNA vaccines for SARS-CoV-2 have occurred after countries began vaccinating adolescents. We undertook a systematic review of cardiac adverse effects associated with SARS-CoV-2 vaccine in children and young people (CYP)< 18 years. Methods Systematic review with protocol prospectively registered with PROSPERO (CRD42021275380). Six electronic databases were searched from 1 December 2019 to 14 September 2021. Eligible studies were those reporting on CYP with reported or proven myocarditis, pericarditis and/or myopericarditis associated with vaccination against SARS-CoV-2. We summarized findings across all clinical cases reported in case report / case series studies. As a number of studies reported data from two publicly available vaccine surveillance systems, we updated estimates of reporting rates for cardiac adverse events up to 31 October for the US Vaccine Adverse Event Reporting System (VAERS) and 13 November for EudraVigilance covering European Union and European Economic Area (EUEA) countries. Results Twenty-one studies were included from 338 identified records. Seventeen were case reports/series describing a total of 127 CYP. Three studies described reporting rates from passive surveillance databases (VAERS, EudraVigilance, and the WHO VigiBase) and one described 22 cases from the US Vaccine Safety Datalink (VSD). Clinical series reported that 99.2% presented with chest pain, 100% had raised troponin and 73.8% had an abnormal ECG. Cardiovascular magnetic resonance (CMR) in 91 cases identified myocardial injury in 61.5%, with 90.1% showing late gadolinium enhancement. NSAIDs were the most common treatment (76.0%). One US dataset (VSD) estimated a significant excess of 29.6 events per million vaccine doses across both sexes and doses. There were 1129 reports of myocarditis and 358 reports of pericarditis from across the USA and EU/EEA. The VAERS reporting rate per million for myocarditis was 12.4 for boys and 1.4 for girls after the first dose, and 49.6 for boys and 6.1 for girls after the second dose. There was a marked trend for VAERS reporting to be highest soon after initiation of the vaccine schedule, suggesting reporting bias. Conclusions Cardiac adverse effects are very rare after mRNA vaccination for COVID-19 in CYP <18 years. The great majority of cases are mild and self-limiting without significant treatment. No data are yet available on children under 12 years. Larger detailed longitudinal studies are urgently needed from active surveillance sources.