The majority of pregnant people in Ontario received the COVID-19 vaccine during its initial release, a study of more than 28,000 pregnancies from 2022 finds.

The study, co-led by McMaster University and the University of British Columbia, used data from ICES, an independent, not-for-profit research institute, for insights into vaccination rates among one of the groups most vulnerable to health complications caused by COVID-19.

The research, published in the Canadian Medical Association Journal this month, determined that about 79 per cent (22,581) people who gave birth in Ontario during the first three months of 2022 received their first COVID-19 vaccine dose, and 75 per cent (21,425) received a second dose by the time they were three months postpartum.

Of those who received a first dose, half did so before they were pregnant and only four per cent delayed it until after they gave birth, demonstrating high uptake for a new vaccine, especially during pregnancy, researchers say.

“It’s encouraging to see this level of vaccination amongst pregnant people because COVID-19 outcomes can be so severe when you’re pregnant,” says Meredith Vanstone, senior author and an associate professor with McMaster’s department of Family Medicine.

“This feels like a public health victory, with people able to access the information they needed to make vaccination decisions from public health sources or clinicians they trust, like their family doctor.”

Another key finding was that pregnant people were slightly less likely to receive the vaccine than non-pregnant females of the same age.

Among the non-pregnant cohort of same-aged female Ontarians, 83 per cent received an initial dose and 80.5 per cent a second during the same period.

Vaccine uptake was lower among younger pregnant people, the study found.

“Throughout the COVID-19 pandemic, misinformation about the vaccines targeted pregnant people, complicating their ability to make well-informed decisions about their health,” said Devon Greyson, first author of the study and assistant professor with the School of Population and Public Health at the University of British Columbia.

“Despite these challenges, it is reassuring to see that so many pregnant people were able to navigate the confusion and ultimately make decisions that protected their health and the health of their babies.”

The researchers used a provincial dataset containing de-identified COVID-19 vaccine records.

“We linked information about people who gave birth during our study and their use of health-care services to understand factors that may be related to COVID-19 vaccine uptake, such as where they live or if they gave birth for the first time,” says Rebecca Correia, a McMaster PhD student who coordinated the data access request and analysis.

“Accessing and linking information for all pregnant and non-pregnant people in Ontario who were eligible for the vaccine makes us more confident in our findings.”

The study was supported by funding from the Canadian Institutes of Health Research (CIHR), a Banting Postdoctoral Fellowship, the Canada Research Chairs program, a Michael Smith Health Research BC Scholar Award and a CIHR/Public Health Agency of Canada Applied Public Health Chair.