U.S. Air Force Kathryn Klein, right, an aerospace medical service specialist with 182nd Medical Group, Illinois Air National Guard, administers an influenza vaccination during drill weekend at the 182nd Airlift Wing in Peoria, Ill., Dec. 8, 2019. According to the Centers for Disease Control and Prevention, the flu is a contagious respiratory illness caused by influenza viruses, and the best prevention is getting a flu vaccine each year. (U.S. Air National Guard photo by Senior Airman Paul R. Helmig II)