**Core Concept**
The discovery of smallpox vaccination is a significant milestone in the history of medicine, marking the first successful use of a vaccine to prevent a disease. Edward Jenner's work laid the foundation for the development of vaccines against other infectious diseases.

**Why the Correct Answer is Right**
Edward Jenner observed that milkmaids who had contracted cowpox, a similar virus to smallpox, were immune to smallpox. He hypothesized that exposure to a related virus could confer immunity to a more virulent disease. In 1796, Jenner conducted an experiment where he inoculated a young boy with material from a cowpox lesion, and later exposed him to smallpox, observing that the boy did not develop the disease. This pioneering work led to the widespread adoption of smallpox vaccination, which eventually eradicated the disease in 1980.

**Why Each Wrong Option is Incorrect**
* **Option A:** Louis Pasteur is incorrect because, while he made significant contributions to vaccination, he did not discover the smallpox vaccine.
* **Option B:** Robert Koch is incorrect because he is best known for his work on the discovery of bacteria and the development of the "gold standard" for identifying bacterial pathogens.
* **Option D:** Jonas Salk is incorrect because he developed the inactivated poliovirus vaccine, but did not discover the smallpox vaccine.

**Clinical Pearl / High-Yield Fact**
The term "vaccine" comes from the Latin word "vacca," meaning cow, which refers to Jenner's use of cowpox to develop the smallpox vaccine.

**Correct Answer: C. Edward Jenner**