I strongly think that parents who elect to not vaccinate their children (absent a documented medical condition preventing safe vaccination) should be liable for child endangerment. This is reckless behavior that is reasonably likely to result in bodily harm to another human being. This is a public safety issue with a clear and benign and effective solution. Those who opt out should be liable for the consequences of their actions.
Good luck going against religious beliefs that curtail vaccinations. That "endangerment" has one hell of an establishment in the community.
There is already precedence in court (US, Canada, and abroad) overruling the objections of Jehova's Witness parents with regard to blood transfusions. A quick Altavista will reveal many cases, as recently as this year (in favor of the child, not the parents). It's not inconceivable that these ruling could extend to cover vaccines as well, if someone (or agency) were to actually bring a lawsuit against the irresponsible parent.