Association of Maternal Influenza Vaccination During Pregnancy With Early Childhood Health Outcomes COMMENT

Vaccination for seasonal influenza is an important health intervention, even for pregnant women. Influenza vaccination helps to reduce the risk of severe influenza illness for the mother and child. However, the uptake of vaccination during pregnancy has been low. Concern around its safety is cited as the leading reason for the low uptake. Although observational studies have found no association between the vaccine and adverse neonatal outcomes, there is a lack of data on its effect on health outcomes in childhood. The aim of this study is to evaluate whether seasonal influenza vaccination in pregnancy results in adverse health outcomes in early childhood. This was a population-based, retrospective study of all live births in Nova Scotia, Canada, from October 1, 2010, to March 31, 2014. The follow-up period began on the child's date of birth untilMarch 31, 2016. The Nova Scotia birth registry linked with physician billing records was used to ascertain whether the mother was vaccinated for seasonal influenza during pregnancy. The outcomes analyzed were immune-related (asthma, infections), non-immune-related (neoplasms, sensory impairment), or all-cause emergency department visits and hospitalizations. A total of 28,255 children were included in the analysis. Of these, 93.4% were followed through the end of the study period, which ranged from 2 to 5.5 years (mean, 3.6 years). The number of children exposed to the influenza vaccine in utero was 10,227 (36.2%). No significant association was observed between vaccination during pregnancy and pediatric asthma (incidence rate, 3.0 vs 2.5 per 1000 person-years; difference, 0.53 per 1000 person-years; 95% confidence interval [CI], -0.15 to 1.21; adjusted hazards ratio [HR], 1.22; 95% CI, 0.94-1.59). There were also no significant associations observed with non-immune-related outcomes (neoplasms: 0.32 vs 0.26 per 1000 person-years; difference, 0.06 per 1000 personyears; 95% CI, -0.16 to 0.28; adjusted HR, 1.26; 95% CI, 0.57-2.78; sensory impairment: 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, 0.49-1.37). After adjusting for confounders, no association was observed between vaccination during pregnancy and all infections (incidence rate, 184.6 vs 179.1 per 1000 person-years; difference, 5.44 per 1000 person-years; 95% CI, 0.01-10.9; adjusted incidence rate ratio, 1.07; 95% CI, 0.99-1.15). It was also not associated with health services utilization (511.7 vs 477.8 per 1000 person-years; difference, 33.9 per 1000 person-years; 95% CI, 24.9-42.9; adjusted incidence rate ratio, 1.05; 95% CI, 0.99-1.16). In conclusion, seasonal influenza vaccination during pregnancy was not associated with increased risk of adverse health outcomes in young children.