COVID-19 mRNA Vaccination in Pregnancy and Risk of Infection in Early Childhood

To examine associations between COVID-19 vaccination during pregnancy and the risk of various infections in early childhood.

We conducted a nationwide, register-based cohort study comprising all live-born infants in Norway between March 2021 and December 2023 with follow-up through 2023. We used Cox regression to estimate hazard ratios for infections diagnosed in primary or specialist health care. Separate analyses were performed for specific infections, including COVID-19.

Among 146 031 infants born in Norway in the study period, 37 013 (25%) were exposed to COVID-19 vaccination in pregnancy. There was no difference in the overall risk of any infection registered in specialist care among offspring exposed to maternal vaccination (adjusted hazard ratio [HR], 0.99; 95% CI, 0.95-1.03). A slightly increased risk of being registered with any infection in primary care was observed among exposed offspring (adjusted HR, 1.05; 95% CI, 1.03-1.07), which was fully attenuated after excluding children of mothers who remained unvaccinated at the end of follow-up. The offspring's protection against COVID-19 decreased over time, and the adjusted HRs for hospital contact were 0.48 for the first 2 months (95% CI, 0.40-0.56), 0.76 at 3 to 5 months (95% CI, 0.60-0.98), 1.13 at 6 to 11 months (95% CI, 0.82-1.56), and 1.14 after 12 months (95% CI, 0.72-1.79). No notable difference in the risk of hospital contacts for infections other than COVID-19 was observed.

COVID-19 vaccination during pregnancy protects the offspring against hospital contact for COVID-19 during the first 6 months of life. No apparent effect was observed for other infections.