COVID-19 Vaccination Reduces Severe Adverse Outcomes in Pregnant Women: JAMA
Covid-19
According to a large Canadian study of nearly 20,000 pregnant women with COVID-19, vaccination significantly reduced severe outcomes. Vaccinated women were 62% less likely to be hospitalized and 90% less likely to require intensive care compared with unvaccinated women. The findings, published in JAMA, also showed a lower risk of early delivery among vaccinated pregnant women, underscoring the protective benefits of COVID-19 vaccination during pregnancy. The study was conducted by Elisabeth M. and colleagues.
In the study, the setting was the collection of data within the CANCOVID-Preg database, which covered pregnant women with confirmed SARS-CoV-2 infections in 9 out of the 13 Canadian provinces and Canadian territories. This data was extracted after the emergence of the Delta variant in Canada on April 5, 2021, when vaccination was recommended among pregnant women, up to the end of 2022, while the outcomes in the newborns were followed into 2023. Outcomes were compared among those vaccinated and those unvaccinated at the time of diagnosis with COVID-19.
Of the 26,584 identified cases, 19,899 pregnant women were found to be eligible for analysis. Infection occurred in the 30-35-year-old group (46.3%), and 55.9% of infections were among Whites. In total, 72% (14,367 cases) of infections were among those who were vaccinated prior to the diagnosis of COVID-19, and 28% (5,532 cases) were unvaccinated. Of the vaccinated group, 80% (11,425 cases) of the infections occurred prior to pregnancy, and 20% (2,942 cases) occurred during pregnancy.
Key findings
The risk of severe maternal illness was significantly lower in vaccinated individuals. For both Delta and Omicron, there was a reduced risk of COVID-19-related hospitalization (risk ratio 0.38, 95% CI 0.30-0.48, ARD 8.7% and risk ratio 0.38, 95% CI 0.27-0.53, ARD 3.8%, respectively) and admission to critical care units (risk ratio 0.10, 95% CI 0.04-0.26, ARD 2.4% and risk ratio 0.10, 95% CI 0.03-0.29, ARD 0.85%, respectively).
Adjusting for comorbidities, both Delta and Omicron remained significantly associated with risk, with risk ratios for hospitalization of 3.82 and 2.43, respectively. Also reduced were the risks of preterm births with vaccination during the variant periods.
Compared with unvaccinated pregnant women during the Delta variant period, vaccinated pregnant women had a 20% reduced risk of preterm births (RR 0.80; 95% CI, 0.66–0.98; ARD 1.8%).
These benefits of vaccination were seen to be much larger during the Omicron variant period; the risk of preterm births was reduced by 36% (RR 0.64; 95% CI, 0.52–0.77; ARD 4.1%).
In this large population-based study, COVID-19 vaccine receipt during or before pregnancy was found to be significantly protective against risks of hospitalization, admission to intensive care units, and risks of preterm birth independently of SARS-CoV-2 virus strain. These findings support existing guidance for vaccine use in pregnancy and confirm the important role that it has to play in safeguarding both maternal and infant health.
Reference:
McClymont E, Blitz S, Forward L, et al. The Role of Vaccination in Maternal and Perinatal Outcomes Associated With COVID-19 in Pregnancy. JAMA. Published online December 15, 2025. doi:10.1001/jama.2025.21001
