COVID-19 vaccination provides consistent protection for pregnant women

Getting a COVID-19 shot prior to or during pregnancy reduces the risks of severe maternal disease outcomes and preterm birth, and this protection remains consistent across different variant periods, according to a study from Canada.

Analysis of large data from the CANCOVID-Preg database showed that among pregnant women who contracted COVID-19 during the Delta wave (5 April 2021 to 20 December 2021), those who were previously vaccinated had lower risks of hospitalization (relative risk [RR], 0.38, 95 percent confidence interval [CI], 0.30–0.48), critical care unit admission (RR, 0.10, 95 percent CI, 0.04–0.26), and preterm birth (RR, 0.80, 95 percent CI, 0.66–0.98) compared with their unvaccinated peers. [JAMA 2026;335:154-162]

The same held true for pregnant women who were infected during the Omicron-predominant period (21 December 2021 to 31 December 2022), with prior vaccination being associated with reduced risks of hospitalization (RR, 0.38, 95 percent CI, 0.27–0.53), critical care unit admission (RR, 0.10, 95 percent CI, 0.03–0.29), and preterm birth (RR, 0.64, 95 percent CI, 0.52–0.77).

Further analysis indicated that the protective effect of prior COVID-19 vaccination on the risk of hospitalization in both variant time periods persisted even after controlling for comorbid conditions.

“The safety and efficacy of COVID-19 vaccines in pregnancy have been well established,” the investigators noted. [Drug Saf 2024;47:991-1010; BJOG 2023;130:348-357]

“New data presented in this analysis pave the way for ongoing vaccine recommendations by demonstrating that the association of vaccination in reducing the risk of adverse outcomes remains substantive,” they said.

The analysis included 19,899 pregnant women infected with SARS-CoV-2. Most infections occurred among those in the 30–35 age group (46.3 percent) and among those of White race (55.9 percent). A small percentage of infections occurred with pre-existing comorbidities, such as asthma (6.2 percent), hypertension (2.2 percent), and diabetes (2.3 percent).

Of the women, 14,367 (72.2 percent) were previously vaccinated and 5,532 (27.8 percent) were unvaccinated. Most women in the vaccinated group (89 percent) contracted infection during the Omicron-predominant period, while most of those in the unvaccinated group (82 percent) were infected during the Delta wave.

In the vaccinated group, 2,942 (20 percent) women received the vaccine during pregnancy, with a median of 18 weeks between vaccination and COVID-19 diagnosis. Compared with the unvaccinated group, the vaccinated group were older, more likely to be White, had lower BMI, and had lower gravidity and parity.

Overall, the data presented in this study provide insights into “the role of vaccine in potentially mitigating the adverse effects of this now common circulating pathogen to inform ongoing care as well as preparedness and response to future respiratory pathogen outbreaks,” the investigators said.