The lasting legacy of seasonal influenza: In-utero exposure and human capital development

Unfavorable circumstances in the fetal period have been shown to have impacts over the entire life course.  Usually, these impacts are identified via catastrophes affecting cohorts such as pandemics, famines, and natural or manmade disasters.  This study is the first to demonstrate long term effects of seasonal influenza, a more moderate threat that recurs every year and is preventable through vaccination.  Using rich administrative data from Denmark, I show that in utero exposure to influenza is associated not only with worse health at birth, but with 10% lower earnings, a 7% decrease in labor market participation, and a strong 43% increase in welfare dependence. The effects are remarkably similar whether they are estimated either at the cohort level, or by tracking offspring of mothers who were known to have been infected.  Birth outcomes are most strongly affected by third trimester exposure, while labor market outcomes are most affected by second trimester exposure.  These findings suggest that influenza exposure has the potential to damage the fetus through multiple mechanisms and that much of the damage on human capital is not visible at birth. Informing mothers, doctors and policy makers about these large economic long-term costs of maternal influenza infections in order to decrease infection rates among pregnant women might have large potential effects on their offspring's human capital development.