SARS-CoV-2 Neutralizing Antibody Responses after Community Infections in Children and Adults

Abstract Background We compared post-infection SARS-CoV-2 neutralizing antibody (nAb) responses among children and adults while the D614G-like strain and Alpha, Iota and Delta variants circulated. Methods During August 2020–October 2021, households with adults and children were enrolled in Utah, New York City, and Maryland. Participants collected weekly respiratory swabs that were tested for SARS-CoV-2 and had sera collected during enrollment and follow-up. Sera were tested for SARS-CoV-2 nAb by pseudovirus assay. Post-infection titers were characterized with biexponential decay models. Results 80 participants had SARS-CoV-2 infection during the study (47 with D614G-like virus, 17 with B.1.1.7, and 8 each with B.1.617.2 and B.1.526 virus). Homologous nAb geometric mean titers (GMTs) trended higher in adults (GMT=2320) versus children 0-4 (GMT=425, p=0.33) and 5-17 years (GMT=396, p=0.31) at 1-5 weeks post-infection but were similar from 6 weeks. Timing of peak titers was similar by age. Results were consistent when participants with self-reported infection before enrollment were included (n=178). Conclusion SARS-CoV-2 nAb titers differed in children compared to adults early after infection but were similar by 6 weeks post-infection. If post-vaccination nAb kinetics have similar trends, vaccine immunobridging studies may need to compare nAb responses in adults and children 6 weeks or more following vaccination.