I feel bad for people who are having to make these decisions, and I don't know any way to say this without it sounding callous, but I don't understand what is served by doing that. They either inject you or they don't. If they don't inject you because you didn't sign the form or because they perceive you don't consent to the medical treatment, you still lose your job if it requires an injection. If they do inject you, then that's also a loss condition if your goal was to leave without being injected.

At best, this is evidence for the lawsuit or human rights tribunal. But that doesn't un-inject you.

The way to avoid getting injected is to avoid going to the place where they inject people, standing in the line marked "wait here to be injected", and sitting there while they put the needle in your arm.