Vaccination effects on reducing COVID-19 complications in pregnancy: A large-scale report from Iran

Objective: The objective of this study was to evaluate the effects of maternal coronavirus disease 2019 (COVID- 19) vaccination on preventing severe complications of COVID- 19 in pregnant women.Methods: A retrospective study was conducted in pregnant women infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV- 2) during pregnancy and/or for up to 6 weeks postpartum between September 1, 2021, to January 30, 2022. The data was retrieved from a national database. The pregnant women were divided into two groups of vaccinated and unvaccinated. The proposed outcomes (the need for hospitalization, intensive care unit admission, and mechanical ventilation and products of conception complications) were compared between the two groups.Results: Approximately 90 000 pregnant women infected with COVID- 19 were included in the study. The data of the vaccinated (19 922) and unvaccinated (70 147) groups were analyzed and compared. Pregnant patients in the vaccinated group had a significantly lower rate of hospitalization (21.2% vs 29.4%) (odds ratio [OR], 0.648 [95% confidence interval (CI), 0.625- 0.673], P = 0.0001) and intensive care unit admission (3.7% vs 7.8%) (OR, 0.453 [95% CI, 0.382- 0.535], P = 0.0001). The need for mechanical ventilation was also lower, although not statistically significant, in the vaccinated group than in the unvaccinated group (30 of 155 [19.4%] vs 418 of 1597 [26.2%]) (OR, 0.677 [95% CI, 0.448- 1.024], P = 0.063). Cesarean section (54.3% vs 58.1%) (OR, 0.856 [95% CI, 0.751- 0.977], P = 0.021) and stillbirth (0.4% vs 3.6%) (OR, 0.097 [95% CI, 0.026- 0.252], P = 0.0001) were also significantly lower in the vaccinated patients. Most pregnant women in the vaccinated group (18 484- 96.14%) received Sinopharm BIBP COVID- 19 inactivated vaccine. No significant differences were seen in the effect of different types of COVID- 19 vaccines on reducing COVID- 19 complications in infected pregnant patients.Conclusion: Maternal COVID- 19 immunization is effective in reducing COVID- 19 complications in infected pregnant women.