QUOTE : On May 14th, 1796, Jenner scratched the arm of a boy named James Phipps, introducing into his skin a droplet of cowpox pus that he had scraped from a blister on the hand of Sarah Nelmes, a dairy worker. He called this pus “the Vaccine Virus”—the word vaccine is derived from the Latin word for cow. The boy developed a single pustule on his arm, and it healed rapidly. A few months later, Jenner scratched the boy’s arm with lethal infective pus that he had taken from a smallpox patient—today, this is called a challenge trial. The boy did not come down with smallpox. Edward Jenner had discovered and named vaccination—the practice of infecting a person with a mild or harmless virus in order to strengthen his or her immunity to a similar disease-causing virus. “It now becomes too manifest to admit of controversy, that the annihilation of the Small Pox, the most dreadful scourge of the human species, must be the final result of this practice,” Jenner wrote in 1801.