Edward Jenner and the smallbox vaccine

At some time in my youth (maybe the 6th grade?) I had to write a paper for school. After consultation with my mother, I decided to write it about Edward Jenner and his development of the smallpox vaccine. I remember that he had noticed that milkmaids were generally immune to smallpox, and went on to discover that it was having contracted cowpox (a similar but milder disease) made them immune. I dreaded the paper, but after I got into the subject, I really enjoyed it. And to this day I remember how that particular vaccine came to be.