COVID-19 mRNA vaccines have been safe for pregnant women, according to observational data from a large Canadian study.
In fact, the pregnant women reported fewer serious health events than non-pregnant women in the 7 days following vaccination and a similar number of events as a control group of unvaccinated pregnant respondents, as researchers led by Manish Sadarangani, DPhil, of the BC Children’s Hospital Research Institute in Vancouver, reported in The Lancet Infectious Diseases.
“Our data provide reassuring evidence that COVID-19 mRNA vaccines are safe in pregnancy,” the group wrote. “Given the increased rate of significant complications related to COVID-19 in pregnancy, high vaccine coverage in this group is important for protection of the pregnant person and young infant.”
The researchers called their study the first to compare pregnant vaccinated, pregnant unvaccinated, and non-pregnant vaccinated women.
“In the early stages of the COVID-19 vaccine rollout there was low vaccine uptake among pregnant people due to concerns about data availability and vaccine safety. There still is lower than average uptake among non-pregnant women of reproductive age,” Sadarangani pointed out in a press statement. “This information should be used to inform pregnant women about the side effects they may experience in the week following vaccination.”
The findings add to a growing body of evidence that COVID-19 mRNA vaccines are safe during pregnancy, noted Sascha Ellington, PhD, and Christine Olson, MD, MPH, both of the CDC, in an accompanying commentary.
“In addition to being safe in pregnancy, other studies have shown that mRNA COVID-19 vaccines are effective at reducing the risk of severe illness in pregnant people and the risk of COVID-19 hospital admission among their infants younger than 6 months,” they wrote, referencing studies in Nature Communications and the New England Journal of Medicine.
The study included a total of 191,360 participants — 5,625 pregnant women and 185,735 non-pregnant women ages 15 to 49 — from seven provinces across Canada who completed the survey between December 2020 and November 2021. Only mRNA vaccine respondents were included.
The participants self-reported health events in the week following their first dose of COVID-19 mRNA vaccination; 94,937 women also reported information after their second dose. Events defined as “significant” were new or worsening health events that caused a respondent to miss school or work, require a medical consult, or be unable to perform daily activities. An emergency department visit or hospitalization was defined as a “serious” health event.
Following the first dose, 4% of the pregnant mRNA-vaccinated respondents reported a significant health event within 7 days, compared with 6.3% of non-pregnant women. From a control group of 339 unvaccinated pregnant women, 11 (3.2%) reported a significant health event in the 7 days prior to completing the survey.
Miscarriage or stillbirth was the most frequently reported serious health event after the first vaccine dose. This event was reported by 2.1% (seven of 339) of unvaccinated pregnant women and 1.5% (83 of 5,597) of vaccinated pregnant women with that data available.
Following dose two, 7.3% of pregnant women reported a significant event compared with 11.3% of non-pregnant women. Serious events were reported in less than 1% of either group.
Multivariable models showed decreased risk to health with mRNA vaccines on the first dose both overall (adjusted OR 0.63, 95% CI 0.55–0.72) and for the two vaccines individually (Pfizer aOR 0.63, 95% CI 0.53–0.75, and Moderna aOR 0.62, 95% CI 0.5–0.77). The same was true for the second dose (overall aOR 0.62, 95% CI 0.54–0.71; Pfizer aOR 0.52, 95% CI 0.41–0.65; Moderna aOR 0.72, 95% CI 0.6–0.85).
“The lower rate of significant health events amongst vaccinated pregnant people, compared with vaccinated non-pregnant individuals, is unexpected and requires more research,” said senior author on the paper Julie Bettinger, MD, also of the BC Children’s Hospital Research Institute.
“Further studies of non-COVID-19 mRNA vaccines are required to identify if the reduced side effects observed in pregnant people in this study is a feature of the mRNA vaccine platform, or of these specific vaccines,” she added.
This work was supported by the COVID-19 Vaccine Readiness funding from the Canadian Institutes of Health Research and the Public Health Agency of Canada CANVAS and by funding from the Public Health Agency of Canada, through the Vaccine Surveillance Reference Group and the COVID-19 Immunity Task Force.
Sadarangani disclosed support via salary awards from the BC Children’s Hospital Foundation, the Canadian Child Health Clinician Scientist Program, and the Michael Smith Foundation for Health Research.
Sadarangani has been an investigator on projects for which his institution received funding from GlaxoSmithKline, Merck, Moderna, Pfizer, Sanofi-Pasteur, Seqirus, Symvivo, and VBI Vaccines.
Bettinger, Ellington, and Olson disclosed no competing interests.
The Lancet Infectious Diseases
The Lancet Infectious Diseases
This content was originally published here.