Edward Jenner, an army surgeon and country doctor from Gloucestershire, England, tried his first experimental vaccination in 1796. At the time smallpox was a fatal disease that mostly affected infants and young children. Jenner recognized that dairymaids infected with cowpox virus (a minor virus that affected cows) were immune to smallpox. He used material from the arm of Sarah Nells, a dairymaid who had contracted cowpox, to infect James Phipps, an eight year old boy. He then exposed Phipps to smallpox, which Phipps did not contract. It worked because cowpox and smallpox have common antigens (proteins), which aroused the young boy’s immune system. After repeating the experiment on other children, including his own son, Jenner concluded that vaccination provided immunity to smallpox without the risk of the person contracting the disease. Jenner used the word “vaccination” for his treatment, which comes from the Latin word vacca, meaning “cow.” Jenner’s findings were published two years later, in 1798, and today vaccines are used around the world to produce immunity to disease.