I generally take the strong consequentialist position that a person who causes A, which later causes B, must be held accountable for B, regardless of whether that person intended to cause B. In short, I broadly claim that factual casuality is moral responsibility.
Therefore, if you stop your child from being vaccinated, I would assert that you are directly to blame for the possible death of your own child and also for the possible deaths of any and all children infected by your child. Moreover, if you advocate refusing vaccinations, you are morally responsible for the deaths of every person who follows your suggestion.
Under this analysis, it looks like I’ll soon be able to claim that Jenny McCarthy is a murderer, because the once eradicated disease measles has started to make a come back in the U. S. recently.