WASHINGTON (AP) — The Pentagon said Friday that there are “active discussions” within the department about making the COVID-19 vaccine booster shots mandatory for service members, even as thousands refuse or seek exemptions from the initial shot requirement.

Pentagon spokesman John Kirby said there have been no final decisions on the matter, but added that Secretary of Defense Lloyd Austin “absolutely encourages people, if they can and if they qualify, to get the booster. But right now there is no requirement for it.”

The defense department in August announced that it would begin requiring all members of the military — including National Guard and Reserves — to get the COVID-19 vaccine. The military services sent out specific guidelines on the mandate, set their own deadlines and laid out the repercussions for those who refused and were not granted a medical, religious or administrative exemption.

Since then, deadlines for the Air Force, Navy and Marine Corps have all passed, and thousands still have not gotten the vaccine or are seeking an exemption, which involves a lengthy process including meetings with commanders, chaplains and medical personnel.

Speaking to reporters at a Pentagon press conference, Kirby said about 96.4% of all active duty personnel have gotten at least one shot. The percentage plunges when members of the National Guard and Reserves are included. Only about 74% of the total military force, including the active duty, Guard and Reserve, are fully vaccinated, but the Army Guard has until next June to get the shots.

Kirby said the numbers are trending in the right direction, but “we know there’s more work to do.”

So far none of the services have said that any service members have been forced out due to their refusal to get the shots, although an unknown number have voluntarily retired or left the service over the matter since the mandate was put in place.

“The secretary’s expectation is 100% vaccination, that’s what he wants to see,” Kirby said.

He added that Austin also expects the services to implement the mandate in a compassionate and thoughtful way and not “immediately go to some sort of punitive or administrative action.” The services, he said, must ensure that troops understand the ramifications of the decision to refuse the vaccine, as well as the ramifications to their health and to their military unit’s readiness.