PC2028: Immunoglobulins in Breast Milk of Women with sars-cov-2 During Pregnancy and Maternal Serum Immunoglobulins at Delivery

Background: The COVID-19 pandemic, caused by the SARS-CoV-2 virus, continues to be a major worldwide public health crisis. Maternal breast milk and breastfeeding are the most effective measures to promote optimal health in newborns. The passage of SARS-CoV-2 antibodies through breast milk has been well established in literature. However, there are no studies that have compared maternal serum immunoglobulins to that found in breast milk. The objective of this study was to determine the presence of immunoglobulins in the breast milk at 2- and 6-weeks post-delivery of women who tested positive to the SARS-CoV-2 virus during pregnancy and compare to maternal serum immunoglobulins at time of delivery.

Methods: This prospective observational cohort study was conducted between April 2020 to January 2021. Approval was obtained from our institutional IRB. We evaluated breast milk collected from mothers who tested positive to SARS-CoV-2 virus during pregnancy. Breast milk IgG and IgA antibody against SARS-CoV-2 S1 RBD protein were evaluated using SARS-CoV-2 S1 RBD protein human IgG and IgA ELISA Kits (IEQ-CoVS1RBD-IgG, IEQ-CoVS1RBD-IgA, RayBiotech, GA, USA). Maternal serum samples were collected and processed based on our previously published study (Song et al, 2021). Data analysis was conducted using Stata 14.2 (Stata Corp, College Station, TX).

Results: A total of 81 breast milk samples were collected from 57 mothers, of which 51 were collected at 2 weeks and 30 were collected at 6 weeks. There were 24 paired samples at 2 and 6 weeks. The maternal and infant characteristics are summarized in Table 1. Breast milk collected at 2 weeks post-delivery was positive for SARS-CoV-2 IgG in 98% and for IgA in 76% of samples. At 6 weeks, breast milk was positive for SARS-CoV-2 IgG in 97% and for IgA in 57% of samples. There was no correlation between the days from first positive PCR test to delivery and breast milk IgG or IgA levels at 2 weeks post-delivery. There was no correlation between maternal IgG levels at delivery and breast milk IgG levels at 2 weeks post-delivery. There was no significant difference in breast milk IgG or IgA positivity when comparing maternal symptoms (asymptomatic, mild/moderately symptomatic, severely symptomatic). While there was no significant difference between the 2- and 6-week values of IgG in the paired samples, there was a significant decrease in the 2- and 6-week values of IgA in the paired samples (Figure 1).

Conclusion: Breast milk of mothers infected with the SARS-CoV-2 virus during pregnancy showed the presence of both IgG and IgA against the virus protein. Breast milk immunoglobulin levels were not related to the maternal IgG levels at delivery or the timing of maternal infection. Continued breastfeeding of mothers infected with SARS-CoV-2 should be encouraged to optimize protective antibodies transferred to the infant.