WASHINGTON, Dec 13 (Reuters) - The U.S. Air Force on Monday said 27 service members had been discharged for refusing to receive a COVID-19 vaccine, the first active-duty troops believed to have been removed for declining the vaccine. The Pentagon made the vaccine mandatory for all service members in August and the vast majority of active-duty troops have received at least one dose. Ann Stefanek, a spokeswoman for the Air Force, said the troops were given a chance to explain why they had refused to get vaccinated, but none of them were given exemptions. About 97% of Air Force personnel are vaccinated against the virus, a number far higher than the general U.S. population. The Air and Space force has about 326,000 active duty personnel. In total, 79 uniformed military personnel across the different services have died from the coronavirus. The United States on Sunday reached 800,000 coronavirus-related deaths, according to a Reuters tally, as the nation braces for a potential surge in infections due to more time spent indoors with colder weather and the highly transmissible Omicron variant of the virus.