Infants of vaccinated mothers less likely to test positive for COVID-19

Infants of mothers vaccinated during pregnancy had a lower risk of positive COVID-19 infection in the first 4 months of life than infants of unvaccinated mothers, according to findings in JAMA Internal Medicine.

The population-based cohort study, based in Norway, included 21,643 live births between September 1, 2021, and February 28, 2022. Nearly half of them (45%, n=9,739) were born to women who received a second or third dose of a COVID-19 during the last 2 trimesters of pregnancy.

Infants of those vaccinated during pregnancy were less likely to test positive for COVID-19 than infants of unvaccinated women, and less likely to test positive during the Delta surge (incidence rate, 1.2 vs 3.0 per 10,000 follow-up days; adjusted hazard ratio, 0.29; 95%CI, 0.19-0.46) than the Omicron surge (incidence rate, 7.0 vs 10.9 per 10,000 follow-up days; adjusted hazard ratio, 0.67; 95%CI, 0.57-0.79).

The study also showed a lower risk of infection among infants born to women who received a third dose of the vaccine than those who only received a second, suggesting a stronger level of protection after a booster dose.

Maternally transferred antibodies are critical in protecting a newborn infant from infection. While recent studies have shown that vaccinated women transfer COVID-19 antibodies in-utero and while breastfeeding, these study results provide further evidence to support the recommendation that pregnant women should receive the COVID-19 vaccine.

Originally published on our sister brand, Contemporary OB/GYN.

Reference:

Carlsen EØ, Magnus MC, Oakley L, et al. Association of COVID-19 Vaccination During Pregnancy With Incidence of SARS-CoV-2 Infection in Infants. JAMA Internal Medicine. Published online June 1, 2022. doi:10.1001/jamainternmed.2022.2442