Multisystemic inflammatory syndrome in children and the BNT162b2 vaccine: a nationwide cohort study

Multisystemic inflammatory syndrome in children (MIS-C) is a rare, severe, post-infectious hyperinflammatory condition that occurs after COVID-19 infection. In this study, we aimed to demonstrate the risk reduction of MIS-C and severe MIS-C after Pfizer–BioNTech BNT162b2 mRNA COVID-19 vaccination. This nationwide cohort study included 526,685 PCR-confirmed COVID-19 cases (age < 19 years), of whom 14,118 were fully vaccinated prior to COVID-19 infection. MIS-C cases were collected from all hospitals in Israel from April 2020 through November 2021. The MIS-C rates were calculated among two COVID-19 populations: positive PCR confirmed cases and estimated COVID-19 cases (PCR confirmed and presumed). Vaccination status was determined from Ministry of Health (MoH) records. The MIS-C risk difference (RD) and 95% confidence intervals (95%CI) between vaccinated and unvaccinated patients are presented. Overall, 233 MIS-C cases under the age of 19 years were diagnosed and hospitalized in Israel during the study period. Among the estimated COVID-19 cases, MIS-C RD realistically ranged between 2.1 [95%CI 0.7–3.4] and 1.0 [95%CI 0.4–1.7] per 10,000 COVID-19 cases. For severe MIS-C, RD realistically ranged between 1.6 [95%CI 1.3–1.9] and 0.8 [95%CI 0.7–1.0], per 10,000 COVID-19 cases. Sensitivity analysis was performed on a wide range of presumed COVID-19 rates, demonstrating significant RD for each of these rates. Conclusion: This research demonstrates that vaccinating children and adolescents against COVID-19 has reduced the risk of MIS-C during the study period. (Table presented.)