Background: 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.
Methods: 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.
Results: 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.
Conclusions: The use of inactivated vaccines during pregnancy induced favorable immune persistence, and the incidence of adverse events did not increase.
Keywords: Coronavirus disease 2019 (COVID-19); immune response; inactivated vaccine; pregnancy; safety.