Measles, mumps, and polio are supposed to be diseases of the past. In the early to mid-20th century, scientists developed vaccines that effectively eliminated the risk of anyone getting sick or dying from illnesses that had killed millions over millennia of human history.

Vaccines, alongside sanitized water and antibiotics, have marked the epoch of modern medicine. The US was at the cutting edge of eliminating these diseases, which helped propel life expectancy and economic growth in the postwar era. Montana native Maurice Hilleman, the so-called father of modern vaccines, developed flu shots, hepatitis shots, and the measles, mumps, and rubella (MMR) vaccine in the 1950s and ’60s, which became virtually universally adopted among Americans.