New study confirms safety and benefits of maternal COVID-19 vaccination for newborns

Toronto, ON, October 23, 2023 – Infants of pregnant women who received an mRNA COVID-19 vaccine during pregnancy had lower risks of severe health outcomes, neonatal death, and neonatal intensive care unit (NICU) admission, according to a new study from researchers at ICES and the University of Toronto.

Published in JAMA Pediatrics, the study included more than 140,000 infants in Ontario, and also showed that newborn and six-month readmissions to the NICU did not increase in infants of mothers vaccinated during pregnancy.

“Our results were consistent across the number of doses someone received during pregnancy, the trimester in which they were vaccinated, and the vaccine product they received, which gives us more confidence that there is no increase in the adverse newborn and infant outcomes we assessed,” says lead author Sarah Jorgensen, a pharmacist, ICES post-doctoral trainee, and PhD candidate at the University of Toronto.

The researchers analyzed linked health records from ICES, and included 142,006 live births in Ontario, Canada, where the mother had received an mRNA vaccination during pregnancy. Expected deliveries between May 1, 2021, and September 2, 2022, were included. In total, 85,670 (60%) of infants were exposed to one or more COVID-19 vaccine doses in utero.

Study findings showed that:

1. Compared with mothers in the unvaccinated group, those who were vaccinated during pregnancy were more likely to: be over 30 years of age; having their first baby; had received a flu vaccine during either of the two previous influenza seasons; and were residents of urban areas and areas with higher incomes.
2. Compared to infants unexposed to the vaccine, those exposed to the vaccine had lower risks of severe health outcomes (7.3% versus 8.3%); neonatal death (0.09% versus 0.16%); and NICU admission (11.4% versus 13.1%).
3. There was no association between maternal vaccination during pregnancy and neonatal readmission to hospital (5.5% versus 5.1%), nor to six-month hospital readmission (8.4% versus 8.1%).

One limitation of the study is that the analyses were restricted to live births, which could mean that the effects of vaccination on miscarriage and stillbirths were not observed. However, studies that have analyzed data from Ontario have not reported an increased risk of miscarriage or stillbirth in women who received COVID-19 vaccines during pregnancy. In fact, some studies found a lowered risk of stillbirth.

“Many women feel nervous about receiving vaccines during pregnancy, but our study will hopefully provide some reassurance on the safety of COVID-19 vaccine during pregnancy for newborns and young infants,” says Jorgensen.

The study, “Newborn and early infant outcomes following maternal COVID-19 vaccination during pregnancy: a population-based retrospective cohort study” was published in JAMA Pediatrics.

Authors: Jorgensen S, Drover S, Fell D, Austin P, D’Souza R, Guttmann A, Buchan S, Wilson S, Nasreen S, Schwartz K, Tadrous M, Wilson K, Kwong J.

ICES is an independent, non-profit research institute that uses population-based health information to produce knowledge on a broad range of healthcare issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting healthcare needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy. For the latest ICES news, follow us on X, formerly Twitter: @ICESOntario

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Misty Pratt
Senior Communications Officer, ICES
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