The 20th century was a dangerous time to be young: a multitude of diseases too often kept children from reaching even their teenage years. Millions suffered and died. From that environment one man would emerge to lead a revolution in vaccine innovation that would save many millions of young lives every year; the greatest scientist of the 20th century, and no one knows his name.. Maurice Hilleman had a singular, unwavering focus: to eliminate the diseases of children. From his poverty-stricken youth on the plains of Montana, Hilleman came to prevent pandemic flu, invent the measles-mumps-rubella (MMR) vaccine, and develop the first-ever vaccine against human cancer. Responsible for more than half of the vaccines children receive today, he is credited with saving more than eight million lives every year.. When parents began choosing not to vaccinate their children in the 1990s, a cruel irony became clear; Hilleman’s unprecedented successes have allowed us to forget just how devastating childhood diseases can be.