The first ever vaccine was created when Edward Jenner, an English physician and scientist, successfully injected small amounts of a cowpox virus into a young boy to protect him from the related (and deadly) smallpox virus. But how does this seemingly counterintuitive process work? Kelwalin Dhanasarnsombut details the science behind vaccines.
Lesson by Kelwalin Dhanasarnsombut, animation by Cinematic.
There are a few inaccuracies, but overall this is a good video.