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One flu over the military.

The Pentagon is once again requiring recruits across all branches of the military to receive flu vaccines, an exception to Defense Secretary Pete Hegseth’s earlier decision to lift the military’s long-standing annual flu vaccine mandate.

This reinstated mandate comes amid news of a flu outbreak at Lackland Air Force Base in Texas. In recent weeks, at least 275 recruits have been diagnosed with influenza, and four have been hospitalized with the virus.

The Air Force confirmed that a recruit died in a military hospital on June 16, but it is unclear if the loss is linked to the flu outbreak.

Democratic Rep. Joaquin Castro of Texas, whose district includes Lackland, told CNN the outbreak “is getting worse.” The situation has become so dire that the Pentagon decided to reverse Defense Secretary Pete Hegseth’s April policy, which made the annual flu vaccine voluntary for the first time in 70 years.

At the time, Hegseth characterized mandatory vaccination as “overly broad and not rational.”

The CDC recommends that everyone 6 months and older get the flu shot every year, even if they’ve been vaccinated or have had the illness in the past.

Hegseth’s April 20 memo rendered the flu shot immediately optional for all US troops.

By early May, though, all military departments had formally requested exemptions to Hegseth’s policy, allowing them to continue requiring flu vaccinations for certain service members, including recruits at boot camp.

“The decisions were based upon thorough risk assessments and are designed to maximize operational readiness, lethality, and force generation, while safeguarding at-risk populations,” Chief Pentagon spokesman Sean Parnell said in a statement.

“The Department remains committed to the health and readiness of our warfighters and civilian personnel.”

However, these exemptions took more than a month to be approved.

“The Department remains committed to the health and readiness of our warfighters and civilian personnel.”

While the Pentagon’s undersecretary, Anthony Tata, approved the request to reinstate the flu shot at basic training on June 11, base officials did not learn that the shots were once again mandatory until June 18 — at which point the outbreak had already begun.

The unit at Lackland has since implemented mitigation measures. They are monitoring trainees who may have been exposed and treating symptomatic trainees with antiviral medications such as Tamiflu.

According to the Department of Defense, when these recruits are cleared by medical professionals, they will resume training.

Hegseth argued that his vaccine policy was designed to “restore freedom and strength” to US forces.

“We’re seizing this moment to discard any absurd, overreaching mandates that only weaken our war-fighting capabilities,” he said in an April 2026 X post.

“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, because your body, your faith, your convictions are not negotiable.”

In the aftermath of Hegseth’s policy change, vaccination among incoming Air Force trainees fell to 40%, according to the New York Times — down from levels that have historically hovered close to 100%.