Edward Jenner is associated with the prevention of smallpox. Smallpox is a highly contagious and deadly disease caused by the variola virus. In the late 18th century, Jenner observed that milkmaids who had contracted a less severe disease called cowpox seemed to be immune to smallpox. Based on this observation, he developed the concept of vaccination. Jenner carried out an experiment by taking material from cowpox blisters and inoculating it into a young boy. The boy developed a mild case of cowpox but later proved to be immune to smallpox. This groundbreaking discovery led to the development of vaccines, which have saved countless lives and led to the eventual eradication of smallpox. Therefore, option 3, Smallpox, is the correct association with Edward Jenner.