Study: COVID vaccine during pregnancy lowers risk of poor infant outcomes

Worried pregnant woman

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The infants of pregnant women given at least one mRNA COVID-19 vaccine dose during pregnancy were at lower risk for poor outcomes, newborn death, and neonatal intensive care unit (NICU) admission, finds a new study from Canada in JAMA Pediatrics.

A University of Toronto–led research team evaluated linked health records from the Institute for Clinical Evaluative Sciences (ICES) on 142,006 live births in Ontario in which the mother was vaccinated against COVID-19 in pregnancy. Singleton deliveries expected from May 2021 to September 2022 were included. A total of 60% of infants were exposed to COVID-19 vaccines in utero.

"Pregnant women have an increased risk of severe COVID-19 compared with their nonpregnant counterparts, and COVID-19 during pregnancy has been associated with fetal and neonatal morbidity and mortality," the study authors wrote. "Vaccination is routinely recommended to protect pregnant women and their newborns from acute respiratory tract infections, such as influenza and pertussis, and pregnant women are designated a priority group for COVID-19 vaccination in multiple countries."

Yet, despite having been demonstrated as safe and protective for both women and their newborns, COVID-19 vaccine uptake has been lower among pregnant women than nonpregnant women in many regions, particularly among younger women and those living in areas with lower socioeconomic status, the authors added.

Lower risk of infant death, NICU admission

Of the 85,670 mothers vaccinated during pregnancy, 48.6% received one dose, 49.6% received two doses, and 1.8% received three. A total of 27,960 women received one or more doses in the first trimester, 45,901 were vaccinated in the second trimester, and 38,410 received their doses in the third trimester.

Relative to unvaccinated mothers, vaccinated mothers were more likely to be older than 30 , having their first baby, had received a flu vaccine during either of the two previous flu seasons, and live in urban areas with higher incomes.

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.

Infants exposed to COVID-19 vaccines were at lower risk for poor outcomes than unexposed infants (7.3% vs 8.3%; adjusted risk ratio [aRR], 0.86) and were less likely to die (0.09% vs 0.16%; aRR, 0.47) or be admitted to a NICU (11.4% vs 13.1%; aRR, 0.86).

Maternal vaccination during pregnancy was not associated with neonatal hospital readmission (5.5% vs 5.1%; adjusted hazard ratio [aHR], 1.03) or 6-month hospital readmission (8.4% vs 8.1%; aHR, 1.01).

Clinician recommendation, easy access can boost uptake

"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," lead author Sarah Jorgensen, PharmD, MPH, of the University of Toronto, said in an ICES news release.

"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," she added.

The study authors noted that because the analysis was limited to live births, the effects of vaccination on miscarriage and stillbirth weren't studied.

In a related editorial, Catherine Healy, MD, of Baylor College of Medicine, and Laura Riley, MD, of Weill Cornell Medicine, noted that the most compelling factor influencing a pregnant woman's decision against being vaccinated is worry about whether it is safe for the newborn. "In this issue of JAMA Pediatrics, Jorgensen and colleagues provide considerable evidence that this concern is unfounded for COVID-19 vaccination," they wrote.

Pregnant women are most influenced by their clinician in terms of vaccine uptake. "For pregnant women, this patient-clinician relationship is particularly strong," Healy and Riley wrote. "When this recommendation is combined with easy access, preferably on-site but at least convenient for uptake during a visit, vaccine administration in pregnancy is most likely to occur."

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