No abstract

Background Multisystem inflammatory syndrome in children (MIS-C), linked to antecedent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, is associated with considerable morbidity. Prevention of SARS-CoV-2 infection or coronavirus disease 2019 (COVID-19) by vaccination might also decrease MIS-C likelihood. Methods In a multicenter case-control public health investigation of children ages 5–18 years hospitalized from July 1, 2021 to April 7, 2022, we compared the odds of being fully vaccinated (two doses of BNT162b2 vaccine ≥28 days before hospital admission) between MIS-C case-patients and hospital-based controls who tested negative for SARS-CoV-2. These associations were examined by age group, timing of vaccination, and periods of Delta and Omicron variant predominance using multivariable logistic regression. Results We compared 304 MIS-C case-patients (280 [92%] unvaccinated) with 502 controls (346 [69%] unvaccinated). MIS-C was associated with decreased likelihood of vaccination (aOR, 0.16 95% CI, 0.10-0.26), including among children ages 5–11 years (aOR, 0.22 95% CI, 0.10-0.52), ages 12–18 years (aOR, 0.10 95% CI, 0.05–0.19), and during the Delta (aOR, 0.06 95% CI, 0.02–0.15) and Omicron (aOR, 0.22 95% CI, 0.11–0.42) variant-predominant periods. This association persisted beyond 120 days after the second dose (aOR, 0.08, 95% CI, 0.03–0.22) in 12–18 year-olds. Among all MIS-C case-patients, 187 (62%) required intensive care unit admission and 280 (92%) vaccine-eligible patients were unvaccinated. Conclusions Vaccination with two doses of BNT162b2 is associated with reduced likelihood of MIS-C in children ages 5–18 years. Most vaccine eligible hospitalized patients with MIS-C were unvaccinated.