Maternal Antibody Response and Transplacental Transfer Following SARS-CoV-2 Infection or Vaccination in Pregnancy

Background: Pregnant persons are at increased risk of severe COVID-19 and adverse obstetric outcomes. Understanding maternal antibody response and transplacental transfer after SARS-CoV-2 infection and COVID-19 vaccination is important to inform public health recommendations.Methods: This prospective observational cohort study included 351 birthing individuals who had SARS-CoV-2 infection or COVID-19 vaccination during pregnancy. IgG and IgM to SARS-CoV-2 S1 receptor binding domain were measured in maternal and cord blood. Antibody levels and transplacental transfer ratios were compared across 1) disease severity for those with SARS-CoV-2 infection and 2) infection versus vaccination.Findings: There were 252 individuals with SARS-CoV-2 infection and 99 who received COVID-19 vaccination during pregnancy. Birthing people with more severe SARS-CoV-2 infection category had higher maternal and cord blood IgG levels (p=0·0001, p=0·0001). Median IgG transfer ratio was 0·87-1·2. Maternal and cord blood IgG were higher after vaccination than infection (p=0·001, p=0·001). Transfer ratio was higher after 90 days in the vaccinated group (p<0·001). Modeling showed higher amplitude and half-life of maternal IgG following vaccination (p<0·0001). There were no significant differences by fetal sex.Interpretation: COVID-19 vaccination in pregnancy leads to higher and longer lasting maternal IgG levels, higher cord blood IgG, and higher transfer ratio after 90 days compared to SARS-CoV-2 infection. Greater infection severity leads to higher maternal and cord blood antibodies. Maternal IgG decreases over time following both vaccination and infection, reinforcing the importance of vaccination, even after infection, and vaccine boosters for pregnant patients.Funding Information: The authors have no conflicts of interest.Declaration of Interests: This work was supported by funding from Friends of Prentice (to JAG) and the Stanley Manne Children’s Research Institute (to LBM). Investigators are supported by National Institute of Allergy and Infectious Diseases at National Institutes of Health [grant number K23 AI139337 to LBM]; and National Institute of Biomedical Imaging and Bioengineering at National Institutes of Health [grant number K08 EB030120 to JAG]. The project benefited from institutional resources supported by the National Center for Advancing Translational Sciences [UL1TR001422].Ethics Approval Statement: This study was approved by the Institutional Review Board of Northwestern University (reference number STU00212232) with a waiver of informed consent was obtained prior to initiation of this research.