SARS-CoV-2 Vaccine-Elicited Antibody Responses in Breastmilk

Abstract

Abstract SARS-CoV-2 mRNA-LNP immunizations significantly reduce severe COVID19. However, our understanding of the immune response within the context of pregnancy and breastfeeding is limited. The overarching goalof this study is to delineate the antibody kinetics, binding breadth, and neutralization capacity of SARS-CoV-2 mRNA-LNP vaccine-elicited antibodies within the breastmilk compartment and compare to serum All participants had detectable IgG in breastmilk. The median serum: breastmilk fold difference of SARS-CoV-2 Spike-specific IgG is 368.2 and 583.51 higher in serum than milk after a first and second dose of vaccine respectively. Concentration of Spike-specific IgG is strongly correlated between serum and milk throughout the study period (Spearman r=0.9429). Although there were no self reported cases of COVID19, 4/13 participants had anti-Nucleoprotein (anti-N) IgG. In participants with anti-N IgG above the cutoff. Vaccination against SARS-CoV-2 induced a 4-fold higher median plasma concentration of anti-Spike IgG compared to participants with no N protein reactivity. The Spike specific IgG in breastmilk was 7-fold higher in participants with anti-N compared to those without anti-N IgG. Pseudovirion neutralization increased with a second dose, and there was a 13-fold median decrease in neutralization at 6 months post dose 1. Post-partum immunization with a SARS-CoV-2 mRNA-LNP vaccine elicits a robust IgG response in serum which is transferred to breastmilk. Serum was able to neutralize pseudovirus after two doses, but neutralization waned in participants without any history of infection. We plan to continue to characterize these antibodies by conducting breastmilk neutralization assays, against the omicron variant NIH: 1 R01-AI161008