There is no law against not vaccinating your child, also, that's not very nice, I like my genes
There's also no law that prevents you from feeding your child nothing but McDonald's Big Macs and ice cream, because it's assumed that if you have a child you posses the standard of responsibility and knowledge of child care to not let your child become extremely obese. But, I mean, hey, that's 'within your right to do' I guess.
That being said, there's also no law that imprisons parents for making a conscious decision to let their child be exposed and vulnerable to poliomyelitis and epidemic parotitis, it's just kinda assumed that you're not going to be a loving dumbass. The reason you are not lawfully obligated to administer vaccines to your children is because in some extremely rare cases some children are born with defects that cause death when combined with vaccine. Not for you to exercise your right to be a dipstuff.