Yes, sometimes people do have severe allergic reactions. However, “severe” reactions like the “life altering… life ending” ones you describe are extremely rare. So your insistence that “many” parents who don’t vaccinate choose not to based on horrible reactions their previous children had is hyperbole at best. Those severe reactions happen so in frequently that the odds of “many” of these anti vaccine parents having had another child suffer life ending consequences is slim. Im sure thats been the experience of some people but not “many” and certainly far from the majority.