Pregnant people who received a COVID-19 vaccine were far less likely to experience severe illness or deliver their babies prematurely, according to a major new UBC-led study published in JAMA .
Drawing on data from nearly 20,000 pregnancies across Canada, the research found that vaccination was strongly associated with lower risks of hospitalization, intensive care admission and preterm birth. These benefits persisted as the virus evolved from the Delta variant to Omicron, which has evolved into newer sublineages that still dominate today.
"Our findings provide clear, population-level evidence that COVID-19 vaccination protects pregnant people and their babies from serious complications," said Dr. Deborah Money, a professor of obstetrics and gynaecology at UBC and senior author of the study. "Even as the virus evolved, vaccination continued to offer substantial benefits for both mother and child."
The study was conducted by the national CANCOVID-Preg surveillance network, led by UBC researchers, and represents one of the largest datasets on COVID-19 and pregnancy worldwide.
The findings revealed that vaccinated people were about 60 per cent less likely to be hospitalized and 90 per cent less likely to require intensive care compared with those unvaccinated at the time of infection. Vaccination was also linked to fewer premature births (deliveries before 37 weeks of pregnancy), reducing the risk by 20 per cent during the Delta wave and 36 per cent during the Omicron wave.
Notably, the analysis found that people vaccinated during pregnancy, as opposed to before pregnancy, had even lower rates of preterm birth and stillbirth.
"There is never a bad time to be vaccinated—whether you're currently pregnant or planning a pregnancy," said Dr. Elisabeth McClymont, lead author and assistant professor in UBC's department of obstetrics and gynaecology. "But our data suggest there may be added benefits to receiving the vaccine during pregnancy."
Informing maternal vaccine guidelines
The findings arrive amid evolving vaccine guidance for pregnant people in some jurisdictions.
In the U.S., the Advisory Committee on Immunization Practices (ACIP) recently did not include a specific recommendation for COVID-19 vaccination during pregnancy in its updated adult immunization schedule. Meanwhile, public health officials in Canada and at the World Health Organization continue to recommend that pregnant people receive a COVID-19 vaccine.
The researchers say their findings provide timely evidence to inform ongoing policy discussions.
"The body of evidence is overwhelmingly clear: COVID-19 vaccination is safe and effective in pregnancy," said Dr. Money. "These latest findings provide critical information for pregnant women and their care providers and strongly support public health guidance that recommends vaccination during pregnancy."
A pan-Canadian effort
The analysis included data from nine Canadian provinces and one territory. Researchers used population-based health data to track outcomes from nearly 20,000 pregnancies affected by SARS-CoV-2 between April 2021 and December 2022.
Even after adjusting for age, body mass index, and pre-existing conditions such as hypertension or diabetes, vaccination remained associated with markedly lower risks of hospitalization.
Beyond COVID-19, researchers say the study underscores the importance of including pregnant people in vaccine research and planning for future respiratory virus outbreaks.
"Pregnancy is a unique period of vulnerability but also of opportunity for prevention," said Dr. McClymont. "This study reinforces how vaccination can make a real difference for maternal and newborn health."
The study was funded by the Public Health Agency of Canada through the COVID-19 Immunity Task Force, the Canadian Institutes of Health Research and the BC Women's Health Foundation.
Interview language(s): English
