THURSDAY, June 25, 2026 (HealthDay News) — The U.S. military is again requiring flu shots for new recruits, just two months after the secretary of defense declared the vaccine optional for troops, as an outbreak at an Air Force training base spreads.
The Army, Navy and Air Force have each been granted exceptions to the new optional annual flu vaccine policy and are once more mandating flu shots for basic trainees, according to officials cited by ABC News.
The reversal comes as cases climb at Lackland Air Force Base, part of Joint Base San Antonio in Texas, and the Air Force's main basic training hub. The case count reached 275 as of Wednesday, up from 222 a day earlier and 159 the week before, ABC News reported. Four people had been hospitalized as of Tuesday.
The outbreak follows an April decision by Defense Secretary Pete Hegseth to make the annual vaccine optional for service members. It had been mandatory for decades.
Even so, individual services have discretion over how orders are carried out, and basic training carries unusual risks. Recruits live in tightly packed bays, shower communally and spend much of the day within arm's reach of one another, ABC News reported.
Illness spreads quickly once a trainee falls ill, and the stress and exhaustion of training can weaken the immune system.
U.S. Department of Defense (DOD) research in 2026 found that recruits are hospitalized for the flu far more often than other troops.
When the outbreak began in early June, about 40% of new Air Force trainees at the base had been vaccinated, according to ABC News. The Air Force now plans to vaccinate every recruit in the current class and all new arrivals.
Additionally, the Army is preparing to extend its requirement to troops deploying overseas, first responders, child care workers, healthcare personnel, prison staff and soldiers in certain large training exercises.
The military has long framed flu vaccination as a readiness issue, aiming to vaccinate more than 90% of active-duty service members each season, a goal it usually meets, according to the DOD.
The shot is no guarantee against infection, but it lowers the odds of serious illness. This season's vaccine cut the risk of a flu hospitalization by about 30% in adults, the U.S. Centers for Disease Control and Prevention reported.
More information
Visit the U.S. Centers for Disease Control and Prevention for more on the current flu season and vaccine recommendations.
SOURCES: ABC News, June 24, 2026; U.S. Centers for Disease Control and Prevention, March 12, 2026; U.S. Department of Defense, influenza hospitalization study, January 2026
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