COVID-19 vaccination during pregnancy reduces severe illness and preterm birth

Researchers have identified significantly reduced odds of severe illness and preterm delivery among pregnant women receiving COVID-19 vaccination, publishing their findings in JAMA.¹

The data also indicated significant reductions in hospitalization and intensive care unit admission risks among pregnant women following COVID-19 vaccine administration. Additionally, these benefits remained between the Delta and Omicron variants, the latter of which has persisted with subvariants through 2025.¹

“Our findings provide clear, population-level evidence that COVID-19 vaccination protects pregnant people and their babies from serious complications,” said Deborah Money, CM, senior author and professor of obstetrics and gynecology at UBC. “Even as the virus evolved, vaccination continued to offer substantial benefits for both mother and child.”¹

Assessing vaccination outcomes

The study was conducted to determine the influence of vaccination on the link between COVID-19 infection in pregnancy with maternal and perinatal outcomes.² The CANCOVID-Preg database was evaluated for population-level data of pregnant patients infected with COVID and their offspring between April 5, 2021, and December 31, 2022.

April 5, 2021, was defined as the start of the Delta variant period, as well as when COVID-19 vaccination began to be recommended in Canada. Nine of 13 Canadian provinces were assessed for cases of COVID-19 diagnosis, and these cases underwent follow-up evaluation for maternal and perinatal outcomes into 2023.²

COVID-19 infection regardless of vaccination status was reported as the primary exposure of the analysis, while primary outcomes included COVID-19-association hospitalization, critical care unit admission, and preterm birth. There were 19,899 cases included in the final analysis, 46.3% of which were among patients aged 30 to 35 years and 55.9% among White patients.²

Reduced hospitalization and ICU admission risks

Vaccination was given to 72% of patients, while 28% were unvaccinated before being diagnosed with COVID-19. In the former group, 80% were vaccinated before pregnancy and 20% during pregnancy. Of cases, 6120 occurred during the Delta period and 13,799 during the Omicron period.²

A significant reduction in hospitalization risk was reported among vaccinated vs unvaccinated patients, with a relative risk (RR) of 0.38 and absolute risk difference (ARD) of 8.7% during the Delta period. These figures were 0.38 and 3.8%, respectively, during the Omicron period.²

For critical care unit admission, vaccinated patients had an RR and ARD of 0.10 and 2.4%, respectively, during the Delta period, vs 0.10 and 0.85%, respectively, during the Omicron period. Preterm birth was also less likely, with the following reductions:²

1. RR of 0.80 during Delta
2. ARD of 1.8% during Delta
3. RR of 0.64 during Omicron
4. ARD of 4.1% during Omicron

Implications

Lower hospitalization odds were reported for the vaccinated group during both periods in multivariable analyses. Unvaccinated patients had an adjusted RR of 2.43 for hospitalization during the Delta period vs 3.82 during the Delta period. Overall, the results highlighted reduced odds of severe disease and preterm birth in women vaccinated during pregnancy.²

“There is never a bad time to be vaccinated—whether you’re currently pregnant or planning a pregnancy,” said Elisabeth McClymont, PhD, lead author and assistant professor in the department of obstetrics and gynecology at UBC. “But our data suggest there may be added benefits to receiving the vaccine during pregnancy.”¹

References

1. COVID-19 vaccination significantly reduces risk to pregnant women and baby. University of British Columbia. December 15, 2025. Accessed December 23, 2025. https://www.eurekalert.org/news-releases/1109419
2. McClymont E, Blitz S, Forward L, et al. The role of vaccination in maternal and perinatal outcomes associated with COVID-19 in pregnancy. JAMA. 2025. doi:10.1001/jama.2025.21001