Those of us over 80 have had real-life experience with these diseases and can hardly believe that anyone would risk their return. It's easy to imagine that diseases like polio, measles and even tetanus are gone forever and can safely be forgotten but, in fact, the infectious diseases haven't changed at all. What has changed is the protection offered by effective vaccines given to the vast majority of our population. Children in countries lacking that protection still experience all of these illnesses and deaths.