THE COVID-19 vaccination offers protective maternal and newborn health benefits for patients who develop SARS-CoV-2 infection in pregnancy, a population-based surveillance study has found. Being vaccinated against COVID-19 was associated with a lower risk of hospitalisation, severe maternal disease and preterm birth, regardless of the COVID-19 variant time period.
The study authors used the CANCOVID-Preg database between April 5 2021 (beginning of the Delta variant time period, and the initiation of recommendations for vaccination in pregnancy in Canada) and December 31 2022 to identify cases. These were based on COVID-19 diagnoses in pregnancy in 9 of 13 Canadian provinces/territories. Cases that occurred through 2022 were followed up into 2023 for pregnancy conclusion and infant outcomes.
COVID-19 vaccinated had a reduced risk of hospitalisation
Of 19,899 database cases that were eligible for analysis, most infections occurred among pregnant mothers aged 30 to 35 years (46.3%), and among those of white race (55.9%). A total of 72% (14,367) of cases were vaccinated and 28% (5,532) were unvaccinated prior to their COVID-19 diagnosis. Among those vaccinated before their diagnosis, 80% (11,425) were vaccinated against COVID-19 prior to pregnancy, and 20% (2,942) were vaccinated during pregnancy.
COVID-19 vaccination was associated with a lower risk of maternal hospitalisation and preterm birth: (Delta: relative risk (RR), 0.38, Omicron: RR, (0.38). Critical care unit admissions (Delta: RR, 0.10; Omicron: RR, 0.10), and preterm birth (Delta: RR, 0.80; Omicron: RR, 0.64) in both the variant time periods.
Vaccination offers mother and infant protection
The study found in multivariable analyses that vaccination continued to be associated with lower hospitalisation risk in both COVID-19 variant time periods after controlling for comorbid conditions. In Omicron cases, compared with the vaccinated group, those unvaccinated had an adjusted relative risk (RR) of hospitalisation of 2.43 (95% CI, 1.72-3.43). In Delta variant cases, those unvaccinated had an adjusted RR of hospitalisation of 3.82 (95% CI, 2.38-6.14).
In summary, vaccination against SARS-CoV-2, both prior to and during pregnancy, is associated with a lower risk of hospitalisation and adverse outcomes for patients who test positive for COVID-19 in pregnancy.
Reference
McClymont E 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.
