Yes and no. This is how vaccines work in the military. They (some office at the DoD) determines what vaccines servicemembers need to have in order to maintain “worldwide deployment readiness” status. This includes the flu shot, which is a yearly requirement for everybody. Some specialized career fields, specific job assignments, or locations may have unique requirements, like yellow fever, anthrax, or smallpox. However, what’s really critical is the deployment readiness thing. You can refuse a vaccine. You can refuse anything you want. That’s fine. Of course it is! But if it’s something they need you to have for your deployment readiness, well, that might keep you from getting to go on that fun assignment to Japan or South Korea. It might prevent you from being able to get any OCONUS base assignment. It might even trigger a medical board, where they’ll review your case and decide that no, if you’re not going to get this vaccination, you cannot maintain deployment readiness status, and you’ll need to be separated. For the good of the unit, don’t you see? I should add that there is usually pressure in situations like this, because the last thing a commander wants or needs are people who can’t be deployed. It messes with manning numbers and fucks with morale, because it means that other people in the unit are going to be hit more often for an out of cycle deployment.