WASHINGTON (AP) — The Air Force became the second military service to approve religious exemptions to the mandatory COVID-19 vaccine, granting requests from nine airmen to avoid the shots, officials said Tuesday.

The nine approved so far represent just a tiny fraction of the more than 6,400 requested by Air Force troops, and they come as other service members are challenging the lack of religious exemptions in court cases. The Marine Corps is the only other military service to grant any religious accommodations, allowing three so far. The Army and Navy have not approved any.

The services have come under criticism for their failure to grant religious exemptions, with members of Congress, the military and the public questioning if the review processes have been fair. Altogether, the services have received more than 14,000 requests for religious exemptions.

Military leaders have argued that religious exemptions to any of the many vaccines troops are required to get have been very rare over the years. Service members are required to get as many as 17 different vaccines, depending on where they deploy.

A federal judge in Texas granted a preliminary injunction last month, stopping the Navy from acting against 35 sailors for refusing on religious grounds to comply with an order to get the COVID vaccine.

Eight of the Air Force approvals came during the initial review process, and one was granted on appeal to senior Air Force leaders. So far, religious exemption requests from more than 3,200 airmen were denied, and another 3,200 are pending.

“The Department of the Air Force determined the service members’ accommodations could be supported with no impact to mission readiness,” the statement Tuesday said.

Defense Secretary Lloyd Austin and military leaders have argued that the vaccine is critical to maintaining military readiness and the health of the force. And all of the services have now either discharged personnel for refusing the vaccine, or put a system in place to do so.

The Marine Corps has discharged 469, the Air Force has discharged 179 and the Navy has discharged 118, according to data released in the last week. The number include active-duty personnel and entry-level recruits who were still in boot camp. The Army has issued more than 3,000 formal letters of reprimand, and fired six soldiers, but has not discharged anyone yet.

All the military services have said the exemption decisions are based not only on the individual request, but also on its impact on the unit, its mission and readiness, and the health and safety of other troops.

Those who get an exemption and are allowed to stay in the service may, however, see an impact on their jobs.

The Navy and the Marine Corps have said unvaccinated service members are not allowed to deploy out to sea on ships, where infections can more easily spread. Those who have approved exemptions — either medical, administrative or religious — are assigned to shore duties.

At least 97 per cent of the troops in each service have gotten at least one shot.