Parents who don't vaccinate their children without a good medical reason should be treated as any other parent who intentionally abuses, harms, mistreats, or abandons their children, simple as that.

If they harm other people on top of that, then that should probably count as attempted murder plus aggravated assault and battery, or some equivalent.

It's a shame that rampant wilful idiocy with intent to cause harm and mayhem isn't a criminal offence, though, because they should also be charged with that.