SARS-CoV-2 Vaccine-Elicited Antibody Responses in Human Milk.

Abstract

Background: SARS-CoV-2 mRNA-LNP immunizations significantly reduce severe coronavirus disease 2019 (COVID-19) disease and have been widely administered throughout the world including those who are pregnant and postpartum. However, our understanding of the immune response within the context of pregnancy and breastfeeding, especially the antibody kinetics and function within the breast milk compartment, is limited. To address this gap, we studied longitudinal blood and breast milk samples from lactating women throughout the primary immunization schedule and for several months after. The overarching goal of this study is to delineate the antibody kinetics, binding breadth, and neutralization capacity of SARS-CoV-2 mRNA-LNP vaccine-elicited antibodies within the breast milk compartment and compare to that in serum.

Methods: We enrolled 13 participants prior to receiving SARS-CoV-2 immunization. We measured anti-SARS-CoV-2 Spike IgG or IgA in serum and self-collected breast milk in participants over a 6-month period. Breast milk was processed by removing lipids and cellular debris by cold centrifugation, and skim milk was then filtered for binding antibody multiplexed assays and neutralization assays.

Results: Postpartum immunization with a SARS-CoV-2 mRNA-LNP vaccine elicits a robust IgG response and moderate IgA response in serum, which is transferred to breast milk. Serum was able to neutralize pseudovirus after completion of the vaccine schedule. These responses persisted for several months predominantly in persons with a potential history of SARS-CoV-2 infection.

Conclusions: Immunization elicits persistent anti-SARS-CoV-2 breast milk antibody responses. We found that hybrid immune individuals had enhanced neutralization and anti-Spike IgG in breast milk and serum. The impact of breast milk antibody on infant anto-SARS-CoV-2 immune responses requires further study.