RESUMO
Understanding the serological responses to COVID-19 vaccination in children with history of MIS-C could inform vaccination recommendations. We prospectively enrolled five children hospitalized with MIS-C and measured SARS-CoV-2 binding IgG antibodies to spike protein variants longitudinally pre- and post-Pfizer-BioNTech BNT162b2 primary series COVID-19 vaccination. We found that SARS-CoV-2 variant cross-reactive IgG antibodies waned following acute MIS-C, but were significantly boosted with vaccination and maintained for at least 3 months. We then compared post-vaccination binding, pseudovirus neutralizing, and functional antibody-dependent cell-mediated cytotoxicity (ADCC) titers to the reference strain (Wuhan-hu-1) and Omicron variant (B.1.1.529) among previously healthy children (n=6) and children with history of MIS-C (n=5) or COVID-19 (n=5). Despite the breadth of binding antibodies elicited by vaccination in all three groups, pseudovirus neutralizing and ADCC titers were reduced to the Omicron variant. Vaccination after MIS-C or COVID-19 (hybrid immunity) conferred advantage in generating pseudovirus neutralizing and functional ADCC antibodies to Omicron.
