If you aren't familiar with the TEDEd series of animated videos, you should be. The series pairs professional educators with top-notch animators to create short video "lessons" on a huge variety of topics in science, medicine and history.
 The latest episode features several of the early attempts to fight smallpox, a disease caused by a highly infectious, often fatal virus that plagued humanity for at least 10,000 years and wasn't fully eradicated until 1979. Physician Edward Jenner (1749–1823) is credited with developing the first vaccine against smallpox, but as the video points out, he probably wouldn't have gotten far without a young boy named James Phipps, a cow and milkmaid Sarah Nelmes.