Do flu shots during pregnancy lead to adverse childhood health outcomes?

The seasonal influenza vaccination is recommended for expectant mothers to reduce the amount of influenza in both the mothers and newborns. There’s been little confirmation on whether this season flu vaccine in pregnancy is linked to adverse childhood health outcomes. A study in JAMA provides needed evidence.¹

The investigators used a birth registry that was linked to health administrative data. It included all live births in Nova Scotia, Canada that occurred between October 1, 2020, and March 31, 2014. Follow-up through March 2016 was included. The outcomes looked for included nonspecific (eg, urgent or inpatient health care utilization), non–immune-related (eg, neoplasms, sensory impairment), and immune-related (eg, asthma, infections), found through emergency department and hospitalization databases.

From a pool of 28,255 children born in the province, 10,227 children were born to mothers who had been given a seasonal vaccination during pregnancy. Over the course of follow-up, which was an average of 3.6 years, the investigators found no significant link between maternal vaccination and neoplasms (incidence rate, 0.32 vs 0.26 per 1000 person-years; difference, 0.06 per 1000 person-years [95% CI, −0.16 to 0.28]; adjusted hazard ratio [HR], 1.26 [95% CI, 0.57 to 2.78]), sensory impairment (incidence rate, 0.80 vs 0.97 per 1000 person-years; difference, −0.17 per 1000 person-years [95% CI, −0.54 to 0.21]; adjusted HR, 0.82 [95% CI, 0.49 to 1.37]), and childhood asthma (incidence rate, 3.0 vs 2.5 per 1000 person-years; difference, 0.53 per 1000 person-years [95% CI, −0.15 to 1.21]; adjusted HR, 1.22 [95% CI, 0.94 to 1.59]). Additionally, there was no significant link seen between maternal influenza vaccination in pregnancy and urgent and inpatient health services utilization (incidence rate, 511.7 vs 477.8 per 1000 person-years; difference, 33.9 per 1000 person-years [95% CI, 24.9 to 42.9]; adjusted incidence rate ratios [IRR], 1.05 [95% CI, 0.99 to 1.16]) and infections in early childhood (incidence rate, 184.6 vs 179.1 per 1000 person-years; difference, 5.44 per 1000 person-years [95% CI, 0.01 to 10.9]; adjusted IRR, 1.07 [95% CI, 0.99 to 1.15]).

The investigators concluded that there were no significant links between a mother’s influenza vaccination during pregnancy and an increased risk of adverse health outcomes in the offspring. The findings ensure that clinicians can continue to recommend the influenza vaccine in pregnancy to provide safe protection for both mother and newborn.

Reference

1. Mehrabadi A, Dodds L, MacDonald N, et al. Association of maternal influenza vaccination during pregnancy with early childhood health outcomes. JAMA. 2021;325(22):2285. doi:10.1001/jama.2021.6778