Rep. Thomas Massie, R-Ky., said in a Twitter post that he has heard from military members who say they intend to leave the service if they are forced to receive the vaccines.
Massie introduced legislation in June that would prohibit any requirement that service members receive a COVID-19 vaccination. The bill currently has 23 cosponsors, including Reps. Marjorie Taylor Greene, R-Ga., Lauren Boebert, R-Colo., and Andy Biggs, R-Ariz.
Rep. Adam Kinzinger, R-Ill., replied to Massie’s tweet, accusing him of "pandering" and noting that service members are required to receive many other vaccinations in order to serve.
Former Rep. Denver Riggleman, R-Va., added that sickness and death both negatively affect military readiness.
Both Riggleman and Kinzinger have U.S. military service experience.
The Army Times reported last week that the service has directed commands to prepare for the administration of mandatory vaccines as early as September.
"Commanders will continue COVID-19 vaccination operations and prepare for a directive to mandate COVID-19 vaccination for service members [on or around] 01 September 2021, pending full FDA licensure," the order said, as reported by the outlet.
A spokesperson for the Department of Defense declined to address whether the vaccine could be made mandatory, saying instead the vaccine remains optional under its Emergency Use Authorization status.
"Shots are voluntary because of emergency-use authorization — DoD is fully complying with U.S. federal code which requires that a vaccine be offered on a voluntary basis while it is available under an EUA from the FDA," the spokesperson said in a statement. "We are focused on making vaccines and information about them available at every level - from the Secretary to the health facilities at the local installations."
Pfizer and Moderna have applied for full authorization, which could allow the military to make the shots mandatory.
A poll conducted by Blue Star Families and the COVID Collaborative of nearly 2,500 military-connected families released in May found that a majority of respondents had been or planned to be vaccinated. Among those who had not yet been vaccinated and hadn’t scheduled appointments, 50% said they did not plan to get the vaccine.
A recent study also showed a higher prevalence of heart inflammation – a condition known as myocarditis – among members of the U.S. military than previously expected. While the cases remained rare, the study found 19 instances among 436,000 second doses administered to male military members. Researchers had been expecting to find eight cases.