HealthDay News — Infants of mothers who received the second or third dose of COVID-19 vaccine during pregnancy have a lower risk of COVID-19 during the first 4 months of life, with lower risk during the delta variant-dominated period, according to a study published online June 1 in JAMA Internal Medicine.

Ellen Øen Carlsen, PhD, from the Norwegian Institute of Public Health in Oslo, and colleagues examined whether COVID-19 vaccination in pregnancy is associated with reduced risk of COVD-19 in infants up to age 4 months during the delta- and omicron-predominant periods. A total of 21,643 live-born infants were included in the register-based cohort study.

The researchers found that 45.0% of the live-born infants were born to women who received a second or third dose of COVID-19 vaccine during pregnancy. The incidence rate of a positive test for SARS-CoV-2 was 5.8 per 10,000 follow-up days in the first 4 months of life. Compared with infants of unvaccinated mothers, infants of mothers vaccinated during pregnancy had reduced risk of a positive test, and lower risk during the delta variant-dominated period than during the omicron period (incidence rate: 1.2 vs 3.0 per 10,000 follow-up days [adjusted hazard ratio, 0.29] during the delta dominated period and 7.0 vs 10.9 per 10,000 follow-up days [adjusted hazard ratio, 0.67] during the omicron dominated period).

“The findings of this study provide early evidence to suggest that infants benefit from passive protection from SARS-CoV-2 infection following maternal COVID-19 vaccination during pregnancy,” the authors write.

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