Comparison of Maternal and Neonatal Antibody Levels After COVID-19 Vaccination vs SARS-CoV-2 Infection

Abstract

ImportancePregnant persons are at an increased risk of severe COVID-19 from SARS-CoV-2 infection, and COVID-19 vaccination is currently recommended during pregnancy.ObjectiveTo ascertain the association of vaccine type, time from vaccination, gestational age at delivery, and pregnancy complications with placental transfer of antibodies to SARS-CoV-2.Design, Setting, and ParticipantsThis cohort study was conducted in Pennsylvania Hospital in Philadelphia, Pennsylvania, and included births at the study site between August 9, 2020, and April 25, 2021. Maternal and cord blood serum samples were available for antibody level measurements for maternal-neonatal dyads.ExposuresSARS-CoV-2 infection vs COVID-19 vaccination.Main Outcomes and MeasuresIgG antibodies to the receptor-binding domain of the SARS-CoV-2 spike protein were measured by quantitative enzyme-linked immunosorbent assay. Antibody concentrations and transplacental transfer ratios were measured after SARS-CoV-2 infection or receipt of COVID-19 vaccines.ResultsA total of 585 maternal-newborn dyads (median [IQR] maternal age, 31 [26-35] years; median [IQR] gestational age, 39 [38-40] weeks) with maternal IgG antibodies to SARS-CoV-2 detected at the time of delivery were included. IgG was detected in cord blood from 557 of 585 newborns (95.2%). Among 169 vaccinated persons without SARS-CoV-2 infection, the interval from first dose of vaccine to delivery ranged from 12 to 122 days. The geometric mean IgG level among 169 vaccine recipients was significantly higher than that measured in 408 persons after infection (33.88 [95% CI, 27.64-41.53] arbitrary U/mL vs 2.80 [95% CI, 2.50-3.13] arbitrary U/mL). Geometric mean IgG levels were higher after vaccination with the mRNA-1273 (Moderna) vaccine compared with the BNT162b2 (Pfizer/BioNTech) vaccine (53.74 [95% CI, 40.49-71.33] arbitrary U/mL vs 25.45 [95% CI, 19.17-33.79] arbitrary U/mL; P < .001). Placental transfer ratios were lower after vaccination compared with after infection (0.80 [95% CI, 0.68-0.93] vs 1.06 [95% CI, 0.98-1.14]; P < .001) but were similar between the mRNA vaccines (mRNA-1273: 0.70 [95% CI, 0.55-0.90]; BNT162b2: 0.85 [95% CI, 0.69-1.06]; P = .25). Time from infection or vaccination to delivery was associated with transfer ratio in models that included gestational age at delivery and maternal hypertensive disorders, diabetes, and obesity. Placental antibody transfer was detectable as early as 26 weeks’ gestation. Transfer ratio that was higher than 1.0 was present for 48 of 51 (94.1%) births at 36 weeks’ gestation or later by 8 weeks after vaccination.Conclusions and RelevanceThis study found that maternal and cord blood IgG antibody levels were higher after COVID-19 vaccination compared with after SARS-CoV-2 infection, with slightly lower placental transfer ratios after vaccination than after infection. The findings suggest that time from infection or vaccination to delivery was the most important factor in transfer efficiency.

Impact of COVID-19 Vaccination on Pregnant Women

“…Vaccine-induced titers were found to be equivalent in pregnant, lactating, and non-pregnant women, suggesting that COVID-19 vaccines transfer antibodies both transplacental and through breast milk and provide context to the mechanisms behind which neonates can secure prolonged immunity. These new findings can be presented as tentative data for additional support for the acceptance of COVID-19 vaccinations in pregnant women [ 31 , 41 , 42 ].…”

“…Though further research is required to identify the extent of this conclusion on humans, as well as its validity, the DART study is a major starting point for easing hesitancy in concerned pregnant patients. Additionally, a recent study found that mRNA vaccines are highly effective in the robust production of SARS-CoV-2-specific antibodies in pregnant women [ 31 , 40 , 41 , 42 ]. Vaccine-induced titers were found to be equivalent in pregnant, lactating, and non-pregnant women, suggesting that COVID-19 vaccines transfer antibodies both transplacental and through breast milk and provide context to the mechanisms behind which neonates can secure prolonged immunity.…”

Evaluation of mRNA-LNP and adjuvanted protein SARS-CoV-2 vaccines in a maternal antibody mouse model

“…Efficiency of matAb transfer to pups, measured as dam:offspring IgG ratio, was ~ 0.57, which is similar to placental transfer ratios of SARS-CoV-2 matAbs in human mother-infant pairs in which the mother received a single dose of SARS-CoV-2 mRNA vaccine < 30 days prior to delivery. 23 Notably in humans, SARS-CoV-2 matAb levels have been shown to be higher after maternal vaccination compared to after maternal infection but maternal vaccination leads to slightly lower placental transfer ratios. 23 Further studies should evaluate if matAbs elicited by SARS-CoV-2 infections versus vaccinations have different inhibitory capacities in mouse models.…”

“…23 Notably in humans, SARS-CoV-2 matAb levels have been shown to be higher after maternal vaccination compared to after maternal infection but maternal vaccination leads to slightly lower placental transfer ratios. 23 Further studies should evaluate if matAbs elicited by SARS-CoV-2 infections versus vaccinations have different inhibitory capacities in mouse models.…”

Australian inflammatory bowel disease consensus statements for preconception, pregnancy and breast feeding

“…Standard antenatal education should include vaccination needs, folic acid supplementation, smoking and alcohol cessation and optimising weight and nutritional status 52 53. COVID-19 and other vaccinations during pregnancy are safe and effective for the new born infants 54. Obstetric and/or maternofetal medicine input may be required for women with complex obstetric histories or comorbidities 49…”