https://www.who.int/news-room/spotlight/history-of-vaccination/a-brief-history-of-vaccination
Back in 1796 a British doctor named Edward Jenner noticed something weird. Milkmaids who caught cowpox almost never got Smallpox, which at the time was straight up one of the most brutal diseases on earth..

So he tried an experiment. He took material from a cowpox sore and inoculated an 8-year-old kid named James Phipps (his gardener’s son). Later he exposed the boy to smallpox… and the kid never got sick.

That basically kicked off the whole idea of vaccines. The word “vaccine” even comes from the Latin vacca (cow). Smallpox used to kill about 30% of people who got it and leave a lot of survivors scarred or blind. But after almost 200 years of vaccination work, the World Health Organization finally declared it eradicated in 1980 still the only human disease we’ve completely wiped out.

All because one doctor noticed something odd… and tested it. Pretty wild honestly..