4. Edward Jenner - Vaccinations
People kick off a lot about vaccines but, ironically, the only reason they're here at all to do this is probably due to vaccination. Jenner is estimated to have saved more than 530 million lives through his work on vaccination. The techniques he pioneered have had one of the biggest influences on disease control in human history. The story of Jenner's discovery has been told so many times that some parts are likely to be apocryphal, but the principle is the same. Jenner worked in a community with lots of dairy farmers in Gloucestershire and, when an epidemic of smallpox hit, he noticed that the cow farmers were not the ones who were getting sick. He figured out that this was because they were contracting the similar, but much milder, disease of cowpox from their bovine charges and that this was somehow offering them protection. Jenner took the pus from the sores of a milkmaid with cowpox and inoculated a local boy with them. Sure enough, the boy came down with cowpox. In a move that was a reckless as it was gross, Jenner then infected the boy with the pus from a smallpox victim. Thankfully for the boy's life and Jenner's criminal record, he stayed healthy and, lo, the first vaccine was made. If you've had your vaccines, breathe a little thanks to Edward Jenner. Even if you haven't, either for medical reasons or "I read a scary article on the internet" reasons, there's a very good chance that you've managed to dodge some of the world's deadliest diseases thanks to a little thing called herd immunity. Rather fitting for a discovery made using cows.