COVID-19 vaccination produces antibodies against the virus, protecting pregnant women, fetuses, and neonates. The goal was to understand immunologic response to vaccines by pregnant women at different trimesters of pregnancy.

To assess maternal blood and cord blood IgG antibody levels against spike protein at delivery in vaccinated pregnant women and in those with COVID-19 infection post-vaccination and to compare immunogenicity profile for different types of COVID-19 vaccine between two groups.

A cross-sectional study was done on 68 pregnant women with 34 subjects in each group. Maternal and cord blood anti-spike IgG antibody measurements were done in the vaccinated group (group 1) and infected after vaccination group (group 2).

Cord anti-spike IgG levels were correlated positively with maternal anti-spike IgG levels (r = 0.935, p < 0.001) in group 1 and 2 (r = 0.638, p < 0.001). Maternal and cord antibody levels and its transfer ratio in the vaccinated group were higher than in group 2, though not significant. Covishield and Covaxin vaccines elicited comparable rises in antibody levels in both groups. Birth weight was significantly different between the two groups (3.0 ± 0.3 vs. 2.7 ± 0.7 kg, p < 0.05).

Maternal IgG antibody levels against spike protein increased at delivery, in both the groups regardless of the gestational age of vaccination. Vaccinated group showed a trend of higher maternal and cord blood antibody levels and antibody transfer ratio to fetus than in the infected after vaccination group. To enhance neonatal antibody levels, pregnant women need not wait until the third trimester for vaccination.