The Defense Department announced Monday that it will move to make the Pfizer COVID-19 vaccine mandatory for all U.S. service members, now that the vaccine has received the full approval of the Food and Drug Administration.

Defense Secretary Lloyd Austin said in a memo to the force this month that he would mandate the vaccine for the 1.3 million service members, either upon FDA approval or by mid-September with a waiver from President Biden. Vaccines have been voluntary for troops while they’re under emergency use authorization. 

Pentagon spokesperson John Kirby told reporters Monday that updated guidance and a timeline for when troops should be vaccinated will be provided in the coming days. 

According to Pentagon data, about 68% of the active duty force is fully vaccinated and 76% have at least one dose. The numbers vary from service to service. As of August 18, 57% of active-duty Marines have been fully vaccinated, 65% of active duty soldiers in the Army, 62% active duty airmen in the Air Force, and 76% of active duty sailors in the Navy. 

“We will also be keeping a close eye on infection rates — which are on the rise now due to the Delta variant — and the impact these rates might have on our readiness,” Austin said in his memo this month. He also urged troops to get vaccinated before a mandate takes effect.  

With the development of emergency-authorized vaccines earlier this year, the Pentagon has been consistently encouraging hesitant troops to get the vaccine. Austin and Chairman of the Joint Chiefs of Staff General Mark Milley have both attended virtual roundtables this year to encourage troops and their families to get the vaccine.

In July, as the highly contagious Delta variant began to surge nationwide, Mr. Biden  tasked Austin with exploring how and when to make the vaccine mandatory for U.S. service members. Austin consulted with medical professionals and announced in an August 9 memo that he would  mandate the vaccine immediately upon FDA approval or by presidential waiver in September. 

In recent weeks, six service members have died of COVID-19, which accounts for about 17% of the total of 35 service member deaths in the Defense Department since the pandemic began.

After months of allowing vaccination to be voluntary, the Pentagon drafted more options because of the rising concern about the Delta variant.