SARS-CoV-2 Vaccine Elicited IgG in Human Milk

Background: Human milk is the main source of nutrition for most neonates as well as a source of components important for neonatal immunity. Neonates have a delay in development of robust immune responses and their immune system is supplemented via milk while the neonatal immune system continues to develop. Eventually, the neonatal immune system begins to function independently of mothers milk and placentally transferred IgG. Aside from missing nutritional benefits, infants who are not breastfed are at a higher risk of developing necrotizing enterocolitis (NEC), pneumonia, and sudden infant death syndrome. While the benefits of human milk in regard to neonatal health are established, the current pandemic brings to question whether or not breastfeeding can prevent disease acquisition in nursing infants. SARS-CoV-2 virus has been detected in human milk however vertical transmission of SARS-CoV-2 appears to be uncommon. Determination of the binding potential of maternal antibodies in the human milk can help us understand how milk can function to protect neonates from SARS-CoV-2 infection. Objectives: To profile the SARS-CoV-2 binding breadth of IgG in milk from vaccinated women on the island of Oahu, Hawaii. Materials and Methods An Institutional Review Board application was submitted and approved by the University of Hawaii Human Studies Program (Protocol number 2021-00090). Participants were given a survey and a human milk collection kit. Fat was removed from milk samples and the skim milk was assessed for IgG composition. Binding towards SARS-CoV-2, SARS-CoV, SARS-CoV-2 variants, and non-pandemic coronavirus antigens was assessed via multiplexed immunoassay. Conclusion Using multiplexed immunoassays, we detect antibodies capable of binding to SARS-CoV-2 Spike of prototype virus as well as novel virus variants which arose through dissemination of wild type SARS-CoV-2 in various geographical spaces during the course of the pandemic. Here we demonstrate that immunization with an emergency use authorization (EUA) SARS-CoV-2 vaccine yields antigen specific and cross-reactive antibody titers within the human milk which may be passed on to nursing infants.NIMHD/NIH-T37MD008636-0