"You mean I didn't HAVE To get sick?"

A friend was telling me about getting her school-age grandson up to date with his immunization schedule. His parents are separated, with one being pro-vaccine and one anti-vaccine. All consent was finally obtained and grandma started the process because the grandson had already suffered from pertussis (whooping cough). When grandma explained the where, why and how of the plan, the grandson said, "you mean I didn't HAVE to get sick?"