Pharmacokinetics of high-titer anti-SARS-CoV-2 human convalescent plasma in high-risk children.

Background While most children experience mild COVID-19, high-risk children with underlying conditions may develop severe disease, requiring interventions. Kinetics of antibodies transferred via COVID-19 convalescent plasma early in disease, have not been characterized. Methods In this study (NCT04377672), high-risk children were prospectively enrolled to receive high-titer COVID-19 convalescent plasma (>1:320 anti-spike IgG; Euroimmun). Passive transfer of antibodies and endogenous antibody production were serially evaluated for up to 2 months after transfusion. Commercial and research ELISA assays, virus neutralization assays, high-throughput phage-display assay utilizing a coronavirus epitope library and pharmacokinetic analyses were performed. Results Fourteen high-risk children (median age 7.5 years) received high-titer COVID-19 convalescent plasma, nine children within five days (range 2-7) of symptom onset and five children within 4 days (range 3-5) after exposure to SARS-CoV-2. There were no serious adverse events related to transfusion. Antibodies to SARS-CoV-2 were transferred from the donor to the recipient, but antibody titers declined by 14-21 days with a 15.1-day t½ for spike protein IgG. Donor plasma had significant neutralization capacity which was transferred to the recipient. However, as early as 30 minutes post-transfusion, recipient plasma had low neutralization capacity. Conclusions Convalescent plasma transfused to high-risk children appears to be safe with expected antibody kinetics, regardless of weight or age. However, current use of convalescent plasma in high-risk children achieves low neutralizing capacity.