Given that the whole purpose of a state is to compel people to do things, I'm wondering what basis you have for drawing the line there. Or why a simple waiver process wouldn't be sufficient to handle those who object.
In general, I would argue that a state has the authority to compel someone into doing anything that has been sufficiently demonstrated to be a good decision, and so the onus is on the anti-vaxxer to show that receiving a vaccine is in fact not a good decision in their case (because it has been shown to be valuable in general.)
In general, I would argue that a state has the authority to compel someone into doing anything that has been sufficiently demonstrated to be a good decision, and so the onus is on the anti-vaxxer to show that receiving a vaccine is in fact not a good decision in their case (because it has been shown to be valuable in general.)