Robert Carpenter, 59th Medical Wing Immunizations Clinic licensed vocational nurse, prepares the San Antonio Military Health System’s first Pfizer COVID-19 vaccine, Dec. 14, 2020, at Wilford Hall Ambulatory Surgical Center, Joint Base San Antonio-Lackland, Texas. Vaccines fight disease by producing an immune response within the body. (U.S. Air Force photo by Airman 1st Class Melody Bordeaux)