Maternal Antibodies Higher After COVID-19 Vaccination vs Infection In Pregnancy

Among women, those who were vaccinated against vs infected with COVID-19 during pregnancy had increased and longer lasting maternal Immunoglobulin G antibodies.

COVID-19 vaccination during pregnancy is associated with increased concentrations of maternal immunoglobulin (Ig) G, cord blood IgG, and higher transfer ratio; however, maternal IgG concentrations decrease over time after both COVID-19 vaccination and infection. These study results were published in Clinical Infectious Diseases.

Researchers conducted a prospective cohort study among women who were infected with or vaccinated against COVID-19 infection during pregnancy. The researchers sought to determine the association between the timing and severity of COVID-19 infection to both maternal and infant antibody concentrations. They also compared antibody concentrations at the time of delivery between patients infected with COVID-19 and those who were vaccinated. Demographics and clinical characteristics, including maternal and infant IgG at delivery and IgG transfer ratio were compared among women infected with COVID-19 during pregnancy.

Among women included in the analysis, 252 were infected with COVID-19 and 99 were vaccinated against COVID-19 infection during pregnancy. The mean (SD) patient age was 32.5 (5.7) years, 52.1% were White, 52.7% had obesity, 11.4% had asthma, and the mean (SD) gestational age at exposure to infection or vaccination was 29.6 (8.9) weeks.

At the time of delivery, 63% of women with infection were positive for IgG antibodies (median, 1.67 antibody units [AU]/mL). The researchers found that increased concentrations of maternal and infant IgG were more likely among COVID-19-infected women with increased disease severity (both P =.001). The median IgG transfer ratio, however, did not significantly vary on the basis of COVID-9 severity (range, 0.87-1.2; P =.29).

Vaccination results in higher transplacental antibody transfer ratios than infection after longer latency.

Among women who were vaccinated during pregnancy, 17% received the first vaccine dose in the third trimester, 83% received the first dose in the third trimester, and 20% received only 1 dose before delivery. Analysis of women in the vaccination vs infected groups showed that the median time between infection onset and delivery was increased compared with the median time between receipt of the first vaccine dose and delivery (66 [IQR, 25-124] vs 46 [IQR, 33-71] days; P =.007). Both maternal (16.64 vs 1.66 AU/mL; P =.001) and infant (17.6 vs 1.28 AU/mL; P =.001) IgG concentrations were significantly higher among women in the vaccinated group vs those in the infected group.

Women in the vaccinated group had both higher and longer lasting maternal IgG and higher infant IgG concentrations compared with those in the infected group, but these concentrations began to decrease in both patient groups at approximately day 50 following delivery.

In both combined and individual analyses of women in the vaccinated and infected groups, no significant differences in concentrations of maternal IgG, infant IgG, or transfer ratio, were noted after adjustment for fetal sex.

Study limitations include the single-center design and the fact that antibody measurements were obtained only once at the time of delivery.

Based on these findings, “Vaccination results in higher transplacental antibody transfer ratios than infection after longer latency,” the researchers concluded.

This article originally appeared on Infectious Disease Advisor


Otero S, Miller ES, Sunderraj A, et al. Maternal antibody response and transplacental transfer following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or vaccination in pregnancy. Clin Infect Dis. Published online November 9, 2022. doi:10.1093/cid/ciac793