Former militaryanon. Military members are REQUIRED to get an annual flu shot in addition to the other shit they stick in you to ensure mission readiness.
For example
>DoD policy is that Military Departments will use the first-available vaccine doses to preserve operational effectiveness, and protect the most vulnerable populations by vaccinating military units that are deployed or will deploy, and other DoD personnel that represent or support critical missions, as well as high risk groups listed in the most current recommendations of the Advisory Committee on Immunization Practices (ACIP).
https://www.nvic.org/faqs/military-vaccines.aspx