Background SARS-CoV-2 infections are frequently milder in children than adults, suggesting that immune responses may vary with age. However, information is limited regarding SARS-CoV-2 immune responses in young children.Methods We compared receptor binding domain–binding antibody (RBDAb) titers and SARS-CoV-2–neutralizing antibody titers, measured by pseudovirus-neutralizing antibody assay in serum specimens obtained from children aged 0–4 years and 5–17 years and in adults aged 18–62 years at the time of enrollment in a prospective longitudinal household study of SARS-CoV-2 infection.Results Among 56 seropositive participants at enrollment, children aged 0–4 years had more than 10-fold higher RBDAb titers than adults (416 vs. 31, P < 0.0001) and the highest RBDAb titers in 11 of 12 households with seropositive children and adults. Children aged 0–4 years had only 2-fold higher neutralizing antibody than adults, resulting in higher binding-to-neutralizing antibody ratios compared with adults (2.36 vs. 0.35 for ID50, P = 0.0004).Conclusion These findings suggest that young children mount robust antibody responses to SARS-CoV-2 following community infections. Additionally, these results support using neutralizing antibody to measure the immunogenicity of COVID-19 vaccines in children aged 0–4 years.Funding CDC (award 75D30120C08737).
Ruth A. Karron, Maria Garcia Quesada, Elizabeth A. Schappell, Stephen D. Schmidt, Maria Deloria Knoll, Marissa K. Hetrich, Vic Veguilla, Nicole Doria-Rose, Fatimah S. Dawood, SEARCh Study Team