At one time, smallpox was a plague that killed 60 million people over the course of a century. By chance, a humble English country doctor named Edward Jenner noticed that dairy workers were never afflicted by the disease after they had a bout of cow pox. He thought that exposing cow pox to the populace would result in immunization to smallpox. As such, he developed what he would call a vaccination, which injected cow pox into the human body. But not being a scientist, this theory was ridiculed by the scientific and medical profession. He had to take a risk, one that could result in life or death, to prove his theory was one that could save the world from death by smallpox.