Meta-Analysis Indicates Safety and Effectiveness of COVID-19 Vaccination During Pregnancy

COVID-19 vaccine effectiveness was high among women who were vaccinated during pregnancy, with a significant positive correlation observed between effectiveness and time since vaccination.

COVID-19 vaccination is safe and effective during pregnancy, and the rate of adverse obstetric and neonatal outcomes is similar between vaccinated and unvaccinated women. These study results were published in Clinical Infectious Diseases.

Nonrandomized controlled trials and observational studies that assessed COVID-19 vaccine effectiveness (VE) and safety during pregnancy were included in this meta-analysis. The primary outcome was the dose- and time-dependent VE of mRNA and inactivated COVID-19 vaccination. Estimates of VE during pregnancy were determined via comparisons between vaccinated and unvaccinated women. Secondary outcomes included obstetric and neonatal adverse outcomes and local and systemic reactogenicity. Nonparametric Mann-Whitney U testing was used to determine the statistical significance of VE on different days.

There were 19 studies included in the meta-analysis, representing a total of 196,609 women.

Among women who received mRNA-based vaccination, VE was lowest (59%; 95% CI, 0.47-0.71) between days 14 and 20 following receipt of the first dose. Similar results were observed between days 21 and 27 (VE, 59%; 95% CI, 0.46-0.72). The researchers noted a VE of 64% (95% CI, 0.29-0.99) among this population at day 28.

In studies with available VE data captured from women who received 2 COVID-19 mRNA vaccine doses during pregnancy, VE was 97% (95% CI, 0.93-1.00) from days 7 to 13 and 96% (95% CI, 0.93-1.00) from days 14 to 56 following receipt of the second dose.

[W]hether the effectiveness of the vaccine differs among pregnant women in the first, second, and third trimesters remains to be evaluated

Analysis via Spearmen correlation showed a significant positive correlation between VE and time since vaccination receipt (P <.005).

No significant associations were noted between COVID-19 vaccination and increased risk for adverse obstetric and neonatal outcomes, including postpartum hemorrhage, miscarriage, stillbirth, placental abruption, and preterm birth. All systemic and local reactions reported among women following vaccination were found to be unrelated to pregnancy.

Limitations of this analysis include potential residual confounding and selection bias.

According to the researchers, “[O]ur findings affirm the certainty of the effectiveness of COVID-19 vaccines in pregnant women,” the researchers noted. However, “[W]hether the effectiveness of the vaccine differs among pregnant women in the first, second, and third trimesters remains to be evaluated,” they concluded.

This article originally appeared on Infectious Disease Advisor


Wu S, Wang L, Dong J, et al. The dose- and time-dependent effectiveness and safety associated with covid-19 vaccination during pregnancy: a systematic review and meta-analysis. Int J Infect Dis. 2023;128:335-346. doi:10.1016/j.ijid.2023.01.018