I heard a story about parents bringing in their child to be immunised against measles.
These parents, on principle, were anti-vaccination - or, at least, opposed to the MMR vaccination, which is designed to protect children from measles, mumps and rubella.
However, it turned out the parents were also very "anti" the idea of taking time off work to look after their child if anyone at their child's school contracted the measles.
You see, schools usually have a policy that unvaccinated children have to go home if there is a risk of catching something at the school.
Historically, "refuseniks" had it easy. They relied on every other kid being vaccinated against disease, so they didn't have to.