Does air pollution make flu season worse?

There are about 25 to 50 million cases of influenza each year, leading to 225,000 hospitalizations and ultimately more than 20,000 deaths yearly. Periods of worse air quality are followed by periods of increased hospitalizations due to influenza. An increase in the EPA’s Air Quality Index of one standard deviation results in approximately a 35% increase in influenza hospitalizations (representing over 27,000 people) during flu season across the United States.

Given disparities in exposure to air pollution across U.S. regions, this may represent a contributing factor for the finding that minority groups in the U.S. have substantially higher influenza hospitalization rates. While fewer than half of Americans receive the influenza vaccine each year, an effective and widespread vaccine can help reduce the dangers of air pollution. A 10% improvement in vaccine use during a year with historically bad pollution would prevent 34.6% of pollution-related influenza hospitalizations.