Historical context and the roots of Jenner's discovery.

May 2016 marks the 220th anniversary of Edward Jenner's first experimental vaccination using cowpox to protect against smallpox. Jenner's discovery, and its rapid adoption around the world, launched a medical revolution that continues to shape how we approach disease prevention. The historical roots of vaccination are found in the popularization of smallpox inoculation during the 18th century, part of an Enlightenment culture that fostered scientific inquiry and the global circulation of knowledge. Jenner was part of that culture and his study of cowpox stemmed from his varied interests as a natural historian, his contacts with leading savants in London, and his medical practice in a flourishing dairy area of England. The amazingly quick spread of vaccination resulted from organized hospital trials in major cities, the severe smallpox epidemic at the turn of the century, disease environment, and policies of European colonial powers.