SARS-CoV-2 Infection Versus Vaccination During Pregnancy: Implications for Placental Antibody Transfer

Maternal antibodies are critical for infant protection. We analyzed the dynamics of placental transferred antibodies generated after SARS-CoV-2 maternal infection and/or vaccination.

Prospective, multicenter, observational study of SARS-CoV-2-infected and/or vaccinated pregnant people and their infants. We collected maternal and cord blood samples at delivery and neonatal/infant samples at delivery, 1, 2, 6 and 12 months of age. Receptor Binding Domain (RBD) and Spike immunoglobulin G antibody titers were measured by Enzyme Linked Immunosorbent Assay (ELISA). Serum maternal cytokines were measured at delivery using the Olink platform. We analyzed differences in antibody transfer according to infection versus vaccination, adjusted for trimester of gestation.

We collected blood samples from 193 pregnant people (infected = 96, vaccinated = 60 and infected and vaccinated = 37) and 154 infants (n = 76, n = 47 and n = 31, respectively). At birth, RBD median (interquartile range) log 10 ng/mL antibody titers of infants from vaccinated-only [4.28 (3.48-4.80)] and from infected-and-vaccinated mothers [4.61 (4.27-4.93)] were higher than from infected-only mothers [2.20 (0.10-3.30); P < 0.001]. Differences persisted through 6 months of age. Median (interquartile range) transplacental antibody transfer ratio was higher in vaccinated-only [2.94 (1.34-3.74)] versus infected-only pregnant people [1.19 (0.33-2.52); P < 0.01]. Spike antibodies showed similar results. Linear regression analysis showed that mean RBD and Spike antibodies transfer ratios were higher in infants from vaccinated-only versus infected-only mothers, adjusted for trimester of infection or vaccination. Maternal concentrations of CXCL10, CXCL11, IL-18 and IFNg at delivery were inversely correlated with placental antibody transfer.

Antibodies generated by maternal vaccination were transplacentally transferred more efficiently and persisted longer in infants than those generated by SARS-CoV-2 infection alone.