1624. SARS-CoV-2 Maternal Vaccination Induces More Efficient Placental Antibody Transfer to Newborns than SARS-CoV-2 Infection During Pregnancy

BACKGROUND: Passive immunization via maternal antibodies (Ab) is a key mechanism for infant protection in early life. This study analyzed the landscape of passive immunization induced by SARS-CoV-2 infection and/or vaccination by comparing the magnitude and durability of the transferred Ab. METHODS: Prospective multicenter observational cohort study of SARS-CoV2-infected and/or vaccinated pregnant women and their infants. We collected maternal and cord blood samples at delivery and neonatal/infant samples at delivery, and at 1, 2, 6 and 12 months (mo) of age. RBD and Spike IgG Ab titers were measured by ELISA. RESULTS: 215 mothers (infected=106, vaccinated=67, infected and vaccinated=42) and 174 infants (n=87, n=54, n=33, respectively) were enrolled. At birth RBD Ab titers median [IQR] of infants from vaccinated mothers [4.28 (3.48-4.80)] log(10) ng/ml and from infected and vaccinated mothers [4.61 (4.27-4.93)] log(10) ng/ml were higher than those from infected mothers [2.20 (0.10-3.30)] log(10) ng/ml, p< 0.001. These differences were observed until 6 mo of age, when only 1/13 (7.7%) infant from infected mothers had detectable maternal Ab compared to 14/15 (93.3%) and 8/8 (100%) from the vaccinated, and infected and vaccinated groups, respectively. At 12 mo none of the infants born to infected mothers had detectable maternal Ab, while in the vaccinated group (n=11), 3 (27.3%) had persistent Ab, and 4 (36.4%) suspected infection. At 12 mo in the infected and vaccinated group (n=6) 3 had no Ab, and 3 had suspected infection. The median [IQR] placental Ab transfer ratio was higher in the vaccinated only group (2.94 [1.34-3.74]) than the infected only group (1.19 [0.33-2.52]) p< 0.01. Linear regression analyses demonstrated that the mean RBD Ab transfer ratio for infants from vaccinated vs infected women was 1.76 (95% CI=1.07-2.88, p=0.025) higher after adjusting for trimester of infection or vaccination. Similar results were observed with Spike Ab. Demographic and clinical characteristics of the study population [Figure: see text] m; median. IQR; interquartile range. N/A; not applicable. [Figure: see text] [Figure: see text] CONCLUSION: Infants from vaccinated mothers demonstrated maternal Ab up to 6 mo with higher titers than infants born from infected mothers. Antibodies generated by vaccination were transferred more efficiently than those generated by infection regardless of the trimester in which occurred. DISCLOSURES: Asuncion Mejias, MD, PhD, MsCS, Astra-Zeneca: Advisor/Consultant|Merck: Grant/Research Support|Pfizer: Advisor/Consultant|Sanofi-Pasteur: Advisor/Consultant Octavio Ramilo, MD, AstraZeneca: Honoraria|Bill & Melinda Gates Foundation: Grant/Research Support|Janssen: Grant/Research Support|Merck: Advisor/Consultant|Merck: Grant/Research Support|Merck: Honoraria|NIH: Grant/Research Support|Pfizer: Advisor/Consultant|Pfizer: Honoraria|Sanofi: Advisor/Consultant|Sanofi: Honoraria