247 - Transfer of Passive Immunity to Newborns after Booster Immunization Against SARS-CoV-2 During Pregnancy in a Predominantly Immigrant Population: A Pilot Study

Publication Number: 1234.247

Marco T. Nunez Ramos, Icahn School of Medicine at Mount Sinai, Rego Park, NY, United States; Adrian M. Adriano, Icahn School of Medicine at Mount Sinai, East Elmhurst, NY, United States; Jennifer L. Pintiliano, Icahn School of Medicine at Mount Sinai, Elmhurst, NY, United States; Sheela Maru, Icahn School of Medicine at Mount Sinai; H+H/Elmhurst Hospital, New York City, NY, United States; Rebecca L. Powell, Icahn School of Medicine at Mount Sinai, New York, NY, United States; Uday P.. Patil, Icahn School of Medicine at Mount Sinai-NYC H+H-Elmhurst, Elmhurst, NY, United States

Background: Maternal immunization against SARS-CoV-2 protects newborns through transplacental transfer of antibodies and via breast milk. Although data on the transfer of passive immunity from mother to newborn after primary vaccination are available in the literature, limited data exist on the effects of booster immunization against SARS-CoV-2 variants during pregnancy and the potential impact of different primary immunization series.

Objective: To assess the transfer of passive immunity to newborns after maternal booster immunization against COVID-19 in a predominantly immigrant population at a New York City Public Hospital.

Design/Methods: In this IRB-approved prospective pilot study, maternal blood, umbilical cord blood, and colostrum were collected from mothers who received the mRNA SARS-CoV-2 booster (Pfizer) during pregnancy (targeting Omicron JN-1 lineage) between March 2024 and March 2025. IgA, IgG, and total secretory antibodies against SARS-CoV-2 spike protein (wild-type and Omicron variant) were measured using Luminex multiplex immunoassays.

Results: A total of 87 samples were collected from a cohort of 30 mother-baby dyads with maternal immigration backgrounds from South-Central America to Asia. The type of primary vaccine varied by country of origin. All participants received the Pfizer mRNA booster, containing the Omicron strain Spike mRNA, during pregnancy. Only three had documented COVID infection, and the average time since the booster was 100 days. Demographic characteristics are shown in Table 1. The immunoassays showed high IgG titers against the Omicron and WT-1 strains in both maternal blood and cord blood. All colostrum samples contained detectable levels of IgA antibodies against both SARS-CoV-2 variants. The results varied with the timing between booster and delivery, with closer proximity to delivery associated with higher antibody responses, suggesting a time-dependent effect. Endpoint titers and titers based on primary series are summarized in Figures 1and 2.

Conclusion(s): Booster vaccination against SARS-CoV-2 during pregnancy with the current mRNA vaccine resulted in a significant elevation of IgG titers in cord blood, indicating effective transplacental transfer of passive immunity. Detection of secretory IgA antibodies in colostrum confirmed reactivation of mucosal immunity. The heterogeneity in titers may be influenced by varying exposure, the type of primary vaccination, the timing of the booster, and individual immune responses.

Table 1.
Demographics

Figure 1
Antibody Titers in Maternal Serum, Umbilical Cord Blood, and Colostrum

Figure 2
Post Booster Antibody Titers Based on Primary Vaccination Type