Who discovered the process of vaccination and in what year did this occur?

The discovery of vaccination is attributed to Edward Jenner, who conducted his groundbreaking work in 1796. Jenner observed that milkmaids who had contracted cowpox, a disease similar to smallpox but less severe, seemed to be immune to smallpox. He hypothesized that exposure to cowpox would provide protection against smallpox and tested this by inoculating a young boy with material taken from a cowpox sore. This method effectively protected the boy from smallpox when he was later exposed to the disease.

Jenner's work laid the foundation for immunology and established vaccination as a viable method for controlling infectious diseases, ultimately leading to the development of vaccines for many other diseases. His findings were influential, making him a pivotal figure in the history of medicine and public health. This significant advancement predates the contributions of other scientists mentioned in the other choices, making this answer the correct one in the context of the vaccination discovery.