The Pentagon said Wednesday that boot camps for all the military services are once again requiring the flu vaccination for all recruits after Defense Secretary Pete Hegseth made the shot optional for the military at the end of April.

The development, confirmed to The Associated Press by a Pentagon official, comes amid a growing, weekslong, flu outbreak at the U.S. Air Force’s boot camp at Lackland Air Force Base that has sickened nearly 300 people. However, the official, who spoke on condition of anonymity to discuss details not cleared for public release, maintained that the permission to mandate the vaccinations was unrelated to the outbreak.

When Hegseth first announced the repeal of the flu vaccine mandate in April, citing “medical autonomy” and religious freedom, he allowed the services to ask for exceptions — or permission to keep the vaccine mandatory — within 15 days of the rollout.