Pregnant individuals who received COVID-19 vaccines experienced fewer severe health complications and reduced rates of premature births, according to a large study led by the University of British Columbia (UBC) and published in JAMA.
The research analyzed data from nearly 20,000 pregnancies across Canada. It found that vaccination was strongly linked with lower risks of hospitalization, intensive care admission, and preterm birth. These protective effects continued as the virus changed from the Delta variant to Omicron and its sublineages.
"Our findings provide clear, population-level evidence that COVID-19 vaccination protects pregnant people and their babies from serious complications," said Dr. Deborah Money, 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 CANCOVID-Preg, a national surveillance network led by UBC researchers. It is one of the largest studies on COVID-19 and pregnancy globally.
Vaccinated individuals were about 60 percent less likely to be hospitalized and 90 percent less likely to need intensive care compared with those unvaccinated at the time they became infected. The risk of premature birth (before 37 weeks) was also reduced: by 20 percent during the Delta wave and by 36 percent during Omicron.
The analysis showed that those vaccinated during pregnancy had even lower rates of preterm birth and stillbirth than those vaccinated before pregnancy.
"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."
These results come as some health authorities update their guidance on COVID-19 vaccination for pregnant people. In the United States, recent recommendations from the Advisory Committee on Immunization Practices did not specifically mention vaccination during pregnancy in its adult immunization schedule. However, Canadian public health officials and the World Health Organization continue to advise pregnant people to get vaccinated.
The authors believe their findings are important for 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."
Researchers collected population-based health data from nine Canadian provinces and one territory covering pregnancies affected by SARS-CoV-2 between April 2021 and December 2022. The study controlled for factors such as age, body mass index, hypertension, or diabetes; even after these adjustments, vaccination remained linked with significantly lower risks of hospitalization.
Beyond immediate findings about COVID-19, researchers highlighted the importance of including pregnant people in future vaccine research related to respiratory viruses.
"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."
Funding came from the Public Health Agency of Canada through the COVID-19 Immunity Task Force, Canadian Institutes of Health Research, and BC Women's Health Foundation.
