The U.S. Navy released updated influenza vaccination guidelines late last week, instructing a select number of service members to get the shot.

The directive comes after Defense Secretary Pete Hegseth announced in April that flu vaccinations for all active-duty, reserve and civilian personnel would be optional.

“The influenza vaccine is highly encouraged to prevent outbreaks that can degrade unit readiness, disrupt training schedules, and deployment execution, which adversely impacts mission,” a Friday Navy administrative message read.

Personnel who are required to receive the annual influenza vaccine include the following groups:

• Service members enrolled in initial entry training programs, such as Officer Candidate School, academy preparatory school, United States Naval Academy, Officer Development School, other officer accession programs, and officers who are directly commissioned
• Navy personnel who work in healthcare and interact with patients
• Navy personnel deployed to countries or theaters that have influenza vaccination requirements
• Navy civilian personnel working in child development and youth services programs
• Navy reserve personnel who administer care to patients and reserve service members who are not involved in patient care but run the risk of exposure to infectious diseases
• Navy reserve personnel who are employed by the Chemical, Biological, Radiological and Nuclear Enhanced Response Enterprise
• Navy reserve personnel operating under Title 10 orders, or those activated for federal active-duty service, who are deployed to theaters requiring vaccination
• Navy reserve personnel on Title 10 orders for “formal military and/or nominative training” in close proximity to areas where service members live or work, such as bases

The administrative message says that service members may be granted vaccine exemptions in accordance with religious accommodations and the discretion of local commanders.

In April, Hegseth said that the cancellation of the previous requirement to receive the flu vaccine was a way to enable the “freedom” of service members, promising that past requirements like the COVID-19 vaccination wouldn’t happen again.

The Defense Department required service members to get the COVID-19 vaccine between Aug. 24, 2021, and Jan. 10, 2023.

More than 8,000 service members who refused the vaccine were involuntarilyy discharged but have been allowed to rejoin the military under the Trump administration.

Two months after Hegseth’s announcement, over 220 trainees at Lackland Air Force Base in Texas were sickened by an influenza outbreak.

A basic military trainee from the 737th Training Support Squadron died on June 16 at Brooke Army Medical Center as a result of the flu, a Texas official said.

Following the outbreak, the Air Force received an exception to vaccinate all trainees.