DoD Making Masks Mandatory Again, Even for the Vaccinated, in Some Places Airmen await takeoff in a C-17 Globemaster III during exercise Nexus Dawn at Travis Air Force Base, Calif., April 24, 2021 (U.S. Air Force/2nd Lt. Daniel Phelps) 28 Jul 2021 The Defense Department on Wednesday resumed requiring all people – including those who have been fully vaccinated against COVID-19 – to wear masks indoors at military facilities in places where the disease is spreading quickly. Deputy Defense Secretary Kathleen Hicks said in a memo that, effective immediately, all service members, federal employees, on-site contractors and visitors must wear masks when indoors in areas of “substantial or high community transmission” of COVID-19, as defined by the Centers for Disease Control and Prevention.