Society and the social compact.
Homo Sapiens, with a few exceptions, is a demonstrably social animal. This means social norms and compacts must be formed amongst diverse groupings of the species.
The overriding factor in all social compacts with social animals is survival of the herd, tribe, or whatever you wish to call the social grouping. The needs of the few or the one must give way to the needs of the herd, or the tribe, or the species, if you will. This basic social compact is a driving factor in all societal needs expressed by the group.
Because of this, as homo sapiens evolved and the collective knowledge of the species increased, vaccinations against horrible life threatening diseases became the norm, and mandatory submission to such vaccinations became a norm of the social compact.
For this reason, and for basic survival of the species, refusal to comply with this social compact demonstrates a decided and specific anti-social behavior. Basic societal survival demands such behavior be altered or those demonstrating such behavior be ejected from the herd, tribe, or society in general.
If you cannot comply with the social compact, you cannot remain a member of society.
It's that simple.