They would catch this highly communicable childhood disease usually between the age of 5 and 9. From 1900 to 1960, with improved sanitation, clean water, and better nutrition fostered by rapid delivery of fresh fruits and vegetables along with affordable refrigerators, the mortality rate from measles in the U.S. dropped more than 95 percent.

When I was a child 70 years ago families would have "measles parties" to expose their kids to another child with measles so they could have the disease and get it over with, since everybody eventually got measles anyway.

With its 3-week course of high fevers, sore throat, conjunctivitis, and a rash spreading from the face down one's arms and legs, the vast majority of children come through the illness unscathed and without complications.  But one particular complication of measles, encephalitis, spurred doctors to develop a vaccine that would provide protection against this disease, like had been done for diphtheria, pertussis (whooping cough), tetanus, and polio.