WASHINGTON, DC – AUGUST 20: U.S. Secretary of Defense Lloyd Austin listens as U.S. President Joe Biden gestures as delivers remarks on the U.S. military’s ongoing evacuation efforts in Afghanistan from the East Room of the White House on August 20, 2021 in Washington, DC. The White House announced earlier that the U.S. has evacuated almost 14,000 people from Afghanistan since the end of July. (Photo by Anna Moneymaker/Getty Images)

U.S. military department heads were ordered on Aug. 24 to “immediately” start getting their troops vaccinated against COVID-19, two days after the first COVID-19 vaccine received full federal approval.

Defense Secretary Lloyd Austin said in a memorandum made public on Aug. 25 that the secretaries of all military departments must “immediately begin full vaccination” of all service members who aren’t already vaccinated.

While a timeline wasn’t laid out in the memo, Austin directed a rapid pace, telling the secretaries to “impose ambitious timelines for implementation.”

Austin announced on Aug. 9 that all active-duty military members would have to get a COVID-19 vaccine. He said he would either wait until a vaccine was approved by drug regulators or, if that didn’t happen by mid-September, he would ask President Joe Biden for a waiver.

The Food and Drug Administration (FDA) gave full approval to the Pfizer-BioNTech shot on Aug. 23.

Austin emphasized in the new memo that the mandatory vaccination would only use vaccines that receive full licensure from the FDA. That means troops will be required to get the Pfizer shot, a Pentagon spokesman said this week.

Approximately 68 percent of the active-duty force, including the National Guard and reserve members, have been fully vaccinated, Pentagon spokesman John Kirby told reporters on Aug. 25. Another 8 percent have had one dose.

The numbers vary by department. Just 40 percent of the Army has been fully vaccinated, compared to 73 percent of the Navy.

Fully vaccinated means a person has received the full vaccination regimen and more than two weeks have elapsed since the last dose. The Pfizer regimen is two doses.

The Pentagon has previously said that members can apply for religious or medical exemptions.

Rep. Don Bacon (R-Neb.), a member of the House Armed Services Committee, said on Aug. 25 that he supports a military vaccine mandate.

The military “can’t have a large percentage of forces unable to deploy because they’re sick,” he said on C-SPAN.

Rep. Seth Moulton (D-Mass.) said on Twitter this week, “This is the right thing to do—for our public health and national security.”

Others have spoken out against a military vaccine mandate, with 31 House members introducing a bill in June that would bar the secretary of defense from mandating COVID-19 vaccines.

“Why force the vaccine on young members of the military who have natural immunity due to a prior infection?” Rep. Thomas Massie (R-Ky.), one of the sponsors, wrote in a recent social media statement.