Military services again requiring recruits to get flu shots as Air Force outbreak grows

In April, Hegseth said the flu shot would be optional for military personnel.

Front view of the Chapman Training Annex entry gate in San Antonio, Texas, Aug. 17, 2024. The Chapman Training Annex is a part of Joint Base San Antonio.

A flu outbreak at the Air Force's basic training hub in San Antonio is worsening, according to two sources familiar with the situation.

As of Tuesday, at least 222 recruits at Lackland Air Force Base, part of Joint Base San Antonio, had been diagnosed with the flu and four had been hospitalized, the two people familiar with the matter told ABC News.

This marks a sharp increase from the 159 cases and two hospitalizations reported last week. The death of one recruit remains under investigation, though it is not yet clear whether it is tied to the outbreak, the sources said.

The outbreak is unfolding just two months after Defense Secretary Pete Hegseth made the annual flu shot optional for troops, scrapping the military's requirement for it, which dates to 1945, a move breaking with longstanding public health directives.

"Our new policy is simple: If you, an American warrior entrusted to defend this nation, believe that the flu vaccine is in your best interest, then you are free to take it; you should. But we will not force you," Hegseth said in April.

Even so, the services have already been given exceptions to Hegseth's policy according to Pentagon spokesperson Sean Parnell in a statement provided to ABC News. As part of those exceptions to the policy, the Army, Navy and Air Force are once again requiring flu shots for basic trainees, according to officials.

In the Air Force, only about 40% of its new trainees at Joint Base San Antonio had a flu vaccination when the outbreak started in early June, according to the two sources.

Front view of the Chapman Training Annex entry gate in San Antonio, Texas, Aug. 17, 2024. The Chapman Training Annex is a part of Joint Base San Antonio. Carlos Kosienski/Sipa USA via Reuters

But with the new exception to policy, the Air Force has the goal of vaccinating all of the recruits in this recruit class and will vaccinate all new recruits arriving at the base according to one of the sources.

Moreover, the Army is preparing in the coming weeks to broaden that requirement to troops deploying overseas, first responders, child care workers, health care personnel, prison staff and soldiers taking part in certain large-scale training exercises, according to a service spokesperson.

While the Pentagon sets policy for the military, the services and its commanders often retain broad discretion to adjust how those directives are carried out, whether to address safety concerns or work around bureaucratic hurdles.

In basic training, troops live in close quarters, sleeping in tightly packed bays, showering communally and spending much of the day within arm's reach of one another as they move through drills, instruction and inspections.

In that environment, illness can quickly spread once one trainee gets sick. Troops are also constantly stressed, and exhausted, conditions which can leave the immune system vulnerable.

Keon McDaniel, the Air Force recruit who died, was in his sixth week of basic training when he experienced a medical emergency on June 12, according to the Air Force. Recruits undergo a medical screening before they can enlist, but that process relies largely on medical history and a relatively limited clinical review.

He was transported to Brooke Army Medical Center, where he subsequently passed away. The cause of the medical emergency is currently under investigation, and a comprehensive medical review is being conducted to determine the facts, according to the Air Force.

The Air Force did not immediately return ABC News' request for comment.

In response to the outbreak, some U.S. officials including Rep. Joaquin Castro -- whose district covers about half of San Antonio, including Lackland Air Force Base -- criticized Hegseth's policy ending mandatory vaccination.

"After Secretary Hegseth scrapped the military's flu vaccine mandate, it was only a matter of time before an outbreak occurred," he wrote in a post on X last week. "It was a reckless decision that put troops in harm's way and undermined our military readiness."

In another post on X, Castro confirmed that the Air Force told his office there were 222 cases of flu at the base. "We need answers," he added.