For a study, researchers sought to describe maternal and umbilical cord blood anti-spike immunoglobulin (Ig)G levels at delivery with coronavirus disease 2019 (COVID-19) vaccination before and during pregnancy, as well as to examine the relationship between prior severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and a vaccine booster dose and anti-spike maternal and umbilical cord IgG levels.

They conducted a retrospective cohort analysis of women who had self-reported COVID-19 immunization (Pfizer-BioNTech, Moderna, or Johnson & Johnson/Janssen) during or before pregnancy, including a booster dose, and delivered at 34 weeks or more. At birth, maternal and umbilical cord blood samples were tested for semi-quantitative anti-spike IgG. Using a rank-sum test, they looked at the relationship between maternal vaccination timing and anti-spike levels in the mother and umbilical cord. A rank-sum test was used to assess the associations between a past history of SARS-CoV-2 infection and maternal and umbilical cord anti-spike IgG levels, as well as the correlations between a booster dosage and maternal and umbilical cord anti-spike levels.

They collected information from 1,359 vaccinated pregnant women, including 20 who had a booster dose, and 1,362 umbilical cord samples. Among completely vaccinated women, maternal anti-spike IgG levels were detectable at delivery regardless of vaccination timing throughout pregnancy; however, early third-trimester vaccination was related with the greatest anti-spike IgG levels in maternal and umbilical cord blood. Maternal and cord blood antibody responses produced with early pregnancy vaccination in women with a history of SARS-CoV-2 infection were equivalent to third-trimester immunization in pregnant women with no history of SARS-CoV-2 infection. In women with or without a history of SARS-CoV-2 infection, a third-trimester booster dose was related to higher levels of maternal anti-spike IgG than third-trimester immunization.

Vaccination against COVID-19 before and throughout pregnancy was related to measurable anti-spike IgG levels in the mother at delivery. The greatest maternal and umbilical cord antibody levels were related to a full vaccination course, a history of SARS-CoV-2 infection, and a third-trimester booster dose.