Air Pollution Increases Influenza Hospitalizations

Gregor Singer; Joshua Graff Zivin; Matthew Neidell; Nicholas Sanders

We next interact our air quality measure with a measure of influenza vaccine effectiveness. Every year, the CDC reports results from small-scale studies of that season's influenza vaccine effectiveness rate by age group (see details in Supplementary Appendix S.1). Based on the histogram in Figure 1c , we use the vaccine effectiveness for the two age groups traditionally susceptible to health complications from influenza: children up to 8 and adults 65 and older. This group comprises 65% of inpatient hospitalization in our data. Figure 3 shows the regression-adjusted relationship between AQI and influenza admissions separately in seasons of low vaccine effectiveness and high vaccine effectiveness for the up to 8-year-old group and 65-year-and-older group, as determined by a median sample split (46). For both age groups, the relationship between air quality and admissions rates flattens and effectively disappears in years of high vaccine effectiveness. Columns (3) and (4) of Table 1 show a similar story using a more continuous measure of vaccine effectiveness. A vaccine effectiveness of 53% for the up to 8year-old group or 34% for the 65-yearand-older group nullifies the link between air pollution and influenza hospitalizations (47).