Receptor-binding Domain Severe Acute Respiratory Syndrome Coronavirus 2-specific Antibodies in Human Milk From Mothers With Coronavirus Disease 2019 Polymerase Chain Reaction or With Symptoms Suggestive of Coronavirus Disease 2019

This study aims to compare the receptor-binding domain (RBD) severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific antibody titers in human milk between mothers with a confirmed coronavirus disease 2019 (COVID-19) polymerase chain reaction (PCR) test and mothers with viral symptoms suggestive of COVID-19. The area under the curve (AUC) for RBD SARS-CoV-2-specific secretory immunoglobulin A (SIgA)/immunoglobulin A (IgA), secretory immunoglobulin M (SIgM)/immunoglobulin M (IgM), immunoglobulin G (IgG), and free secretory components (fSC) in milk samples from eight mothers with a confirmed COVID-19 PCR, eight mothers with viral symptoms (no PCR testing), and six unexposed mothers (pre-pandemic 2018). AUCs of RBD SARS-CoV-2-specific SIgA/IgA, SIgM/IgM, IgG, and fSC in milk samples were comparable between mothers with confirmed COVID-19 PCR and mothers with viral symptoms of suggestive COVID-19. AUCs of RBD-specific SIgA/IgA, IgG, and fSC were higher in the COVID-19-exposed group than in the unexposed group, and SIgM/IgM tended to be higher in the exposed mothers. In conclusion, women with viral symptoms suggestive of COVID-19 could secrete antibodies and fSC specific to SARS-CoV-2 in human milk.