448 - Evolution of Anti-SARS CoV-2 Antibody Responses in Breast Milk in a Newborn Intensive Care Unit Population During the Course of the COVID Pandemic: 2020-2022

Breastfeeding provides protection to neonates against infectious diseases through the transfer of maternal antibodies, especially IgA.


Objective: Our research goals were: 1) to examine the prevalence of IgG and IgA antibody (ab) to SARS-CoV-2 spike (S) protein in breast milk (BM) and newborn serum in a NICU population in Minneapolis, MN; and 2) to evaluate ab prevalence over a two-year period spanning the COVID pandemic (2020-2022).

Design/Methods: This NICU study population consisted of 69 consented mothers: 65 BM samples were available for analysis, for pregnancies resulting in 87 deliveries (12 pairs of twins, 3 sets of triplets and 54 singletons). For 45/65 (69%) pregnancies, matched infant sera were available. Anti-COVID ab in BM samples was compared to corresponding infant sera, to evaluate for transplacental ab transfer. Medical records were reviewed to examine maternal COVID vaccination/disease history.

Results: First, we determined SARS-CoV-2 ab prevalence in milk, using IgG and IgA assays (SARS-CoV-2 Spike protein serology, Cell Signaling Technology). The prevalence of BM anti-COVID Ig was 45/65 (69%). BM was IgG+/IgA+ for 26 mothers; IgG+/IgA- in 12 samples; IgG-/IgA+ in 7; and IgG-/IgA- in 20 (Fig. 1). Next, we evaluated for transplacental serum ab transfer by ELISA, using a 6XHis-tagged S (RBD domain) target antigen (DOI: 10.1002/cpmc.100). Sera were available for 45 pregnancies. Transplacental ab was present in 22/31 (71%) mother-infant dyads with corresponding Ig-positive BM, but only 3/14 (21%) sera with Ig-negative BM (P=0.003, Fisher exact). We next compared the prevalence of SARS-CoV-2 serum ab for two time periods during the COVID pandemic: “early pandemic” (EP), from 12/2020 – 9/2021, and “late pandemic” (LP), 10/2021 – 4/2022. Sera were ELISA-positive in 11/30 (37%) EP pregnancies, whereas ELISA was positive in 14/15 (93%) LP pregnancies (P=0.0003; Fig. 2). There was a correlation between transplacental ab prevalence and a confirmed history of maternal COVID vaccination, particularly for LP newborns (Fig. 3).

Conclusion(s): The overall prevalence of anti-SARS-CoV-2 ab in BM in our NICU cohort was approximately 70% over the course of the COVID pandemic. Interestingly, there was discordance between BM and serum ab: ~30% of Ig-positive BM were in dyads in which corresponding infant sera were ab-negative. Measurement of BM Ig, rather than serum ab, may be a more useful biomarker in assessing COVID risk in breast-feeding infants in the NICU. We observed a significant evolution of ab seroprevalence over the course of the pandemic, corresponding to implementation of COVID vaccination.