You don't vaccinate your kid, knowing that you're endangering your child and other children, and another child contracts a preventable disease from your child and dies because of it. Assuming the parents of the other child could prove that the child had spread it to theirs, the parent would be morally and legally responsible, if the parents were to press charges. Possible charges include child endangerment, criminal negligence (which in this case is very similar to child endangerment) and manslaughter. (Disclaimer: I'm not a certified E-Lawyer™ and these are just educated guesses based off what I found on the internet.)
Those are educated guesses but here's a good anology, if my father does not give me a vaccination for the flu, and I get a small child sick from the flu because I did not have the vaccination, and that small child is not developed to where it has a strong immune system yet and it dies. I ask you, is my father to be charged with manslaughter?
Poll