The case of the English physician and surgeon Edward Jenner (1749-1823) is one of perseverance and method, but also of an audacity that today would have put him behind bars. Contrary to what is sometimes presented, the idea of vaccinations did not arise as a “eureka” moment. In Jenner’s epoch, variolation, or inoculation, was practiced using smallpox scabs or pus in healthy people to protect them from what was then a terrible plague.