There is no law that states you must vaccinate your child. So, it is up to the parents. It is not considered negligent when a child is not vaccinated and childrens services can not interfere in this case.
However, in case of divorce, where both parents have equal rights, either one can take the child to a doctor and get the child vaccinated.
If it is brought up in a divorce that one parent wants to vaccinate and the other doesn't the judge will most likely rule in favor of the vaccine seeking parent. I don't think it can influence custody however.
This is a good time to remind people that the spouse who is on the fence but goes along with not vaccinating the child, should be the one to sign the vaccine exemption for school/day care. Just in case....