ABSTRACT
Problem: Despite being over 3 years into the pandemic, infants remain highly undervaccinated and at a high risk for hospitalization due to COVID-19. Further investigation as to how maternal health decisions for immunization can reduce morbidity from infant COVID-19 by providing passive immunity is necessary. The objective of this study was to describe the rates of SARS-CoV-2 variant antibody transfer from mother to infant cord blood by trimester ofmaternal vaccination. Methods of study: This is an observational cohort study including mother-infant dyads receiving primary or subsequent booster COVID- 19 vaccines during pregnancy.Unvaccinated, but SARS-CoV-2 infected dyads with were included as a comparison group. We quantified median titer and interquartile range (IQR) for SARS-CoV-2 receptor binding domain (RBD) IgG in infant cord blood samples at delivery using the mesoscale discovery platform (electrochemiluminescence). Primary outcome was infant cord IgG titer by trimester of vaccination for the WA1/2022 RBD IgG and current circulating, immune evasive XBB RBD IgG. Secondary outcome is the percent detectable IgG for each variant. Sensitivity analysis was performed based on known SARS-CoV-2 infection. Result(s): Eighty-three mother-infant dyads were included in this analysis. Seven were vaccinated in the first trimester, 37 in the second trimester, 33 in the third trimester, and 6 were unvaccinated and infected. Twenty-three (30%) of the vaccinated group had known SARS-CoV-2 infection. Most received monovalent mRNA COVID-19 vaccines during pregnancy, aside from two who received the viralvectored Ad26.COV2.S, and two received the bivalent mRNA vaccine during pregnancy. The median cord blood WA1/2020 RBD IgG titer was 5370 (412-7296) for first, 1225 (589-3289) for second, 2623 (664-5809) for third trimester in individuals who received aCOVID-19 vaccine dose during pregnancy, and 45 (10-187) in those unvaccinated and infected. After excluding thosewith infection, the cord blood IgG was 514 (106-4182), 1070 (518-2317), and 2477 (664-4470) for first, second, and third trimester, respectively. The rate of detectable WA1/2020 RBD IgG was 100% for all three trimesters, even when excluding infected individuals. For theXBBvariant, cord bloodRBDIgG titer was 284 (43-1296) for first, 66 (32-227) for second, 173 (45-389) for third trimester, and 10 (10-11) in the unvaccinated/infected group. Excluding infections, the cord blood XBB RBD IgG was 54 (10-128), 44 (25-181), and 152 (45-360) for first, second, and third trimester vaccination, respectively. The rate of detectable XBB IgG in those who received a vaccine during pregnancy were 83%, 91%, and 90% for first, second, and third trimester respectively, compared to 17% in the unvaccinated/infected group. Excluding infections, the rate of XBB RBD IgG detection was 66%, 89%, and 95% for first, second, and third trimester vaccination, respectively. Conclusion(s): Vaccination during pregnancy leads to high rates of detectable cord blood IgG specific to SARS-CoV-2 WA1/2020 variant and current circulating variants (XBB), regardless of trimester of vaccination. Infection history leads to higher cord blood IgG in vaccinated;however, infection alone without vaccination leads to lower titer and greater rates of undetectable cord IgG at delivery.