2) What's his story?
1) intereted in science, agriculture, farming, astronomy, etc.
In 1798, smallpox was running rampant and wiping out millions of people. What Jenner noticed was that his milkmaids, and he himself, were not getting smallpox. The people milking the cows start out with no legions on their hands. They get legions after milking cows, whcih goes away, leaving no scarring.
If they get these legions, they don't get smallpox.