SARS-CoV-2 neutralizing antibody titers in maternal blood, umbilical cord blood, and breast milk

ObjectiveWe quantified neutralizing SARS-CoV-2 antibody against spike protein (nAb) levels after vaccination and SARS-CoV-2 infection in maternal serum, cord blood, and breast milk and determined whether they correlate with levels of spike protein binding antibody.Study designWomen (n = 100) were enrolled on admission for delivery. Previous SARS-CoV-2 infection was defined by anti-nucleocapsid antibodies. Levels of nAb and binding antibodies against spike receptor binding domain were measured in maternal blood, cord blood, and milk.ResultsMaternal nAb levels were higher after vaccine and infection than vaccine alone but waned rapidly. Levels of nAb in cord blood and milk correlated with maternal levels and were higher in cord blood than maternal. Spike protein binding antibody levels correlated with nAb.ConclusionSARS-CoV-2 vaccination near delivery may boost antibody-mediated immunity in the peripartum period. Neutralizing antibodies are passed transplacentally and into milk. Spike protein binding antibody may be a feasible proxy for nAb.

Automated summary

This study quantified the levels of neutralizing SARS-CoV-2 antibodies in maternal serum, cord blood, and breast milk after vaccination and infection. The levels of neutralizing antibodies in cord blood and milk correlated with maternal levels and were higher in cord blood. Spike protein binding antibodies may serve as a feasible proxy for neutralizing antibodies.