When Externalities Collide: Influenza and Pollution

Influenza and air pollution are significant public health risks with large economic consequences shared across the globe. The common etiological pathways through which they harm health present an interesting case of compounding risk via interacting externalities. Using regional and temporal variation in pollution and disease transmission, we find exposure to more air pollution significantly increases influenza hospitalizations. By exploiting the random deviations in influenza vaccine effectiveness over time, we show high influenza vaccine effectiveness neutralizes this relationship. This suggests seemingly disparate policy actions of pollution control and expanded vaccination provide greater returns than found when studied in isolation.