Immune response and safety of inactivated SARS-CoV-2 vaccines during pregnancy: a real-world observational study

As pregnant women are excluded from clinical trials of inactivated SARS-CoV-2 vaccines, it is important to assess the immune response in women receiving the vaccination while unknowingly pregnant.

In a multicenter cross-sectional study, we enrolled 873 pregnant women aged 18-45 years. Serum antibody levels induced by inactivated vaccines were determined. Adverse events were collected by self-reported survey after vaccination. Logistic regression model and restricted cubic spline model were used to investigate the association of factors with antibody positivity.

As the doses of the vaccine increase, neutralizing antibody (NAb) positivity was 98.3%, 39.5%, and 9.5% in pregnant women, respectively. The dose of vaccine and duration since vaccination were associated with NAb positivity. The OR of two and three doses of vaccines were 7.20 and 458.33 (P < 0.05). NAb levels and duration since vaccination showed a linear relationship in pregnant women vaccinated two doses, with a decrease to a near seropositivity threshold at 22 weeks. Adverse events were mainly mild or moderate after vaccinated during pregnancy, with no increase in incidence compared with whom vaccinated during pre-pregnancy.

The use of inactivated vaccines during pregnancy induced favorable immune persistence, and the incidence of adverse events did not increase.