1094. Multisystem Inflammatory Syndrome in Children (MIS-C) in Persons Fully Vaccinated with Two Doses of mRNA COVID-19 Vaccine Compared with Persons with Partial or No Vaccination Reported, U.S. National MIS-C Surveillance

Abstract Background CDC began collecting COVID-19 vaccination status of persons with MIS-C as part of national surveillance in May, 2021. We describe and compare MIS-C in fully vaccinated persons with MIS-C in persons with partial or no vaccination reported. Methods We identified COVID-19 vaccine age-eligible persons meeting the CDC MIS-C case definition reported by health departments as of March 28, 2022 and divided them into 3 groups for this analysis: 1) fully vaccinated (receipt of a 2-dose mRNA primary vaccine series with MIS-C onset ≥28 days after vaccine dose 2 to account for the delay between infection and MIS-C), 2) partially vaccinated (MIS-C onset after dose 1 or < 28 days from dose 2 or receipt of Janssen [Johnson & Johnson] vaccine and 3) no vaccination reported. We compared characteristics between the groups. Results Of 7,880 MIS-C cases reported, 1,085 were vaccine eligible: 45 were fully vaccinated, 64 partially vaccinated, and 976 had no vaccine reported. Demographic characteristics were similar, although the Northeast had the lowest percentage of persons with vaccination not reported (Table). Though not statistically significant, fully vaccinated persons less frequently had severe cardiac involvement (67% vs 74%), shock (33% vs 44%), severe hematologic involvement (47% vs 54%), and mucocutaneous involvement (53% vs 63%) compared with those with no vaccine reported (Table). Forty-four percent of those fully vaccinated required ICU-level care vs 59% with no vaccine reported (p=0.053). Nineteen (2%) of those without vaccine reported died; no fully or partially vaccinated persons died. Table.Demographic and clinical characteristics of individuals with MIS-C with COVID-19 vaccine not reported compared to partially and fully vaccinated individuals Conclusion Persons who acquire SARS-CoV-2 infection after being fully vaccinated can develop MIS-C, with similar clinical characteristics to those with no vaccination reported. A lower but not statistically significant percentage of fully vaccinated persons required ICU-level care compared with those without vaccination, and there were no deaths in the fully vaccinated group. These data do not account for trends in MIS-C over time, including the influence of circulating SARS-CoV-2 variants on MIS-C clinical manifestations. We will continue to evaluate these comparisons as the sample size of reported MIS-C cases increases. Disclosures All Authors: No reported disclosures.