I'm old enough to have had measles, mumps and rubella as a child, and to have experienced the excitement of my parents when the Salk vaccine for polio was announced. It is totally bonkers for people to be blase about diseases that are horrible to experience even when you don't end up with one of the more dire outcomes. I was extremely sick for weeks when I had measles and mumps was enormously painful. Most adults remember having chickenpox, which presents in a variety of ways, but plenty of people don't escape with a mild case. That mother is a lunatic.