Edward Jenner is a giant of modern medicine. Throughout history, smallpox had plagued humanity with disfigurement, blindness and death. It was an incurable blight, the suffering of which Jenner helped to end.
Surmising from the immunity of milkmaids that cowpox might be some defence against the ravages of smallpox, in 1793 he took some of the matter from a human case of cowpox and inserted it into...