Edward Jenner was born in Berkeley, Gloucestershire on 17th May 1749.
At the age of 14, he was apprenticed to a local surgeon, and later moved to St. George's Hospital in London to complete his medical training. After that, he became a local doctor to his home town.
It was well known that milkmaids never contracted smallpox. However, they often contracted cowpox, a much tamer version of the disease.
After Sarah Nelmes contracted cowpox, Jenner determined that she could not catch smallpox.
James Phipps was chosen to confirm this method of immunization. He was infected by cowpox, and then was found to be immune to smallpox. This was the first of many experiments to develop vaccination against smallpox.
Later in Jenner's life, his method of vaccination replaced a more dangerous version. It became widespread and was required by English and Welsh law 30 years after Edward Jenner's death.