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Military services are once again requiring flu vaccinations for basic trainees after a flu outbreak at Lackland Air Force Base in San Antonio, Texas, worsened significantly in recent weeks. The Army, Navy, and Air Force have received exceptions to Defense Secretary Pete Hegseth's April policy making flu shots optional for troops, according to Pentagon spokesperson Sean Parnell.
As of Tuesday (June 24), 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, two sources familiar with the situation told ABC News. This marks a sharp increase from the 159 cases and two hospitalizations reported last week. The death of one recruit, Keon McDaniel, remains under investigation, though it is not yet clear whether it is tied to the outbreak.
McDaniel was in his sixth week of basic training when he experienced a medical emergency on Thursday, June 12. He was transported to Brooke Army Medical Center, where he subsequently passed away, according to the Air Force.
The outbreak is unfolding just two months after Hegseth scrapped the military's requirement for annual flu shots, a policy that dated back to 1945. "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.
In the Air Force, only about 40 percent of new trainees at Joint Base San Antonio had a flu vaccination when the outbreak started in early June. 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.
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.
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.
The 37th Training Wing, which is housed at Lackland, trains more than 36,000 troops per year.
According to an October 2025 Armed Forces Health Surveillance Division report, the vaccine helped prevent the flu's impact among older service members and can assist in protecting the overall health of the military, especially in recruit stations, which have the highest rates of flu infections every year. The report found that the highest cumulative hospitalization rate among active-duty service members occurred in individuals 25 years old and younger.
Medical personnel are monitoring trainees who were in close contact with sick members for symptoms, and symptomatic trainees are receiving care with antiviral medications, such as Tamiflu. Trainees can return to training once they are cleared by medical professionals, according to an Air Force 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. Under Secretary of Defense for Personnel and Readiness Anthony Tata told senators in May the department solicited input from the services, which responded with "a robust set of exception" requests.