Vaccination linked to lower risk for hospitalization, critical care unit admission, preterm birth during delta and omicron periods
FRIDAY, Dec. 19, 2025 (HealthDay News) — During the delta and omicron variant time periods, vaccination against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) prior to and during pregnancy was associated with a lower risk for severe maternal disease, according to a study published online Dec. 15 in the Journal of the American Medical Association.
Elisabeth McClymont, Ph.D., from the University of British Columbia in Vancouver, Canada, and colleagues examined the impact of vaccination on maternal and perinatal outcomes associated with SARS-CoV-2 infection in pregnancy. Data were included for pregnant individuals infected with SARS-CoV-2 and their infants between April 5, 2021, and Dec. 31, 2022, during the delta and omicron variant time periods.
The analysis included 19,899 cases, identified based on COVID-19 diagnoses in pregnancy. The researchers found that 72 and 28 percent of cases were vaccinated and unvaccinated, respectively, prior to their COVID-19 diagnosis. Among those vaccinated prior to diagnosis, 80 and 20 percent were vaccinated before and during pregnancy, respectively. Vaccination was associated with a lower risk for hospitalization (relative risks, 0.38 and 0.38 during delta and omicron, respectively), critical care unit admission (relative risks, 0.10 and 0.10 during delta and omicron, respectively), and preterm birth (relative risks, 0.80 and 0.64 during delta and omicron, respectively). After controlling for comorbid conditions, vaccination was associated with lower hospitalization risk in both variant time periods. Those unvaccinated had an adjusted relative risk for hospitalization of 2.43 and 3.82 in omicron and delta, respectively.
“Vaccination against SARS-CoV-2 prior to and during pregnancy, before COVID-19 diagnosis, was associated with a lower risk of severe maternal disease and preterm birth regardless of variant time period,” the authors write.
Several authors disclosed ties to the biopharmaceutical industry.
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