Signals Detected for Myocarditis, Seizures in Children After COVID-19 Vaccination

Myocarditis or pericarditis and seizures in children can occur at higher rates compared with historical rates for these conditions following COVID-19 vaccination, according to study findings published in JAMA Network Open.

Researchers conducted a cohort study to examine 21 prespecified health outcomes among children in the US aged 6 months to 17 years following their receipt of 1 of 3 ancestral monovalent COVID-19 vaccines (BNT162b2, mRNA-1273, or NVX-CoV2373).

The researchers sourced data from 3 commercial claims databases in the US and supplemented with vaccination data from Immunization Information Systems. Increased rates of each health outcome were compared with annual historical rates from January to December 2019, January to December 2020, and April to December 2020. Due to the lack of sufficient sample size for historical rates, 6 of the 21 health outcomes were only monitored descriptively. Monthly sequential testing was executed using Poisson Maximized Sequential Probability.

A total of 4,102,016 patients (boys, 50.2%; urban residence, 95.1%) were included in the study, 3,920,563 (95.6%) of whom received the BNT162b2 vaccine, 174,427 (4.3%) of whom received mRNA-1273, and 53 (<0.1%) of whom received NVX-CoV2373.

Demographics among mRNA vaccine recipients were similar across vaccine brands aside from age at first dose; while the majority of BNT162b2 recipients were aged 5 years and older (93.4%), the majority of mRNA-1273-vaccinated patients were aged younger than 5 years (97.6%).

Among the 15 health outcomes that were sequentially tested, only 2 met the threshold for a statistical signal. These 2 outcomes included myocarditis or pericarditis post-BNT162b2 vaccination in patients aged 12 to 15 and 16 to 17 years, as well as seizure after vaccination with BNT162b2 and mRNA1273 in children aged 2 to 4 and 2 to 5 years.

In a post hoc sensitivity analyses, a statistical signal for seizure was detected following mRNA-1273 vaccination when using 2019 background rates, but not when using 2022 rates.

Further signal characterization activities were not conducted for the myocarditis or pericarditis outcome because of the established link between myocarditis or pericarditis and COVID-19 mRNA vaccination.

The evaluation of the statistical signal for seizure in children aged 2 to 4 and 2 to 5 years revealed no issues with data quality. Out of 72 observed seizure cases among children aged 2 to 4 and 2 to 5 years, 70.8% were classified as febrile seizures. Timing of seizures did not indicate substantial clustering and the median time between vaccination and diagnosis was 2 days.

Study limitations included potential bias and confounding, reduced generalizability of results, and the inability to evaluate most demographic factors.

“Near-real-time monitoring detected a previously identified statistical signal for myocarditis or pericarditis and a new statistical signal for seizure; however, these results should be interpreted cautiously because the methods only screened for potential statistical signals and have several limitations,” the researchers concluded.

Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.