Impact of Maternal Vaccination on Antibody Transfer and Protection of Infants

Influenza is an important cause of illness and morbidity for infants. Seasonal influenza vaccination during pregnancy protects infants; however, the precise influence of maternal vaccination and how vaccine-elicited antibodies provide protection in some but not all infants is incompletely understood. We comprehensively profiled the transfer of functional antibodies and defined humoral correlates of immunity against influenza in a clinical trial of maternal influenza vaccination. Influenza-specific antibody subclass levels, Fcɣ receptor (FCGR) binding levels, and antibody-dependent innate immune functions were all profiled in the mothers during pregnancy and at birth, and in cord blood. Vaccination increased influenza-specific antibody levels, antibody binding to FCGR, and specific antibody-dependent innate immune functions in both maternal and cord blood, with FCGR binding most enhanced via vaccination. Influenza-specific FCGR binding titers were lower in cord blood of infants who subsequently developed influenza infection. Collectively these data suggest that in addition to increased antibody titers, the selective transfer of FCGR-binding antibodies contributes to the protective immune response in infants against influenza.