Air Force flu outbreak at Lackland grows, vaccine mandate returns

The flu outbreak at Lackland Air Force Base in San Antonio reached at least 222 cases and four hospitalizations, and the Air Force moved to require flu shots again for basic trainees. The illness has spread through the 37th Training Wing over the past three weeks, hitting a pipeline that sends more than 36,000 recruits through the unit each year.

The reversal came less than two months after Defense Secretary Pete Hegseth announced on April 21, 2026, that annual flu vaccines would no longer be mandatory for U.S. military personnel. Hegseth described the old policy as “overly broad and not rational.” Now, the Army, Navy and Air Force have each been granted exceptions so basic trainees can again be required to get the shot. Pentagon spokesman Sean Parnell and officials familiar with the change said so.

At Joint Base San Antonio, the problem was compounded by weak uptake before the mandate changed. About 40% of roughly 1,700 new Air Force trainees had been vaccinated last week, leaving most recruits vulnerable as they moved through close quarters, shared training spaces and the constant turnover that defines basic training. The Air Force said its goal is to vaccinate every recruit in the current class and all new arrivals at the base.

The outbreak has also unfolded against the backdrop of a recruit’s death. Keon McDaniel, of the 737th Training Support Squadron, died June 16 at Brooke Army Medical Center. Officials said the cause remains under investigation and have not said whether it was tied to the flu outbreak.

Rep. Joaquin Castro of Texas, whose district includes Lackland, said Hegseth’s decision to scrap the flu vaccine mandate was reckless and that it undermined military readiness.

Air Force medical professionals and public health officials have isolated symptomatic trainees and treated them with antiviral medications such as Tamiflu while continuing to monitor the situation.