Edward Jenner noticed that milkmaids with cow-infected pox did not get sick by THE pox, so he correctly assumed that it was protecting them. So his "vaccination" was simply infecting healthy people with this harmless pox, and PRESTO, they did not get sick.
Later vaccinations were more advanced and a bit different, - I still remember how sick I got from mine.
Now Pasteur was another story. He was well ahead of everybody in his time in research of infections. It was him that vaccinated successfully against rabies, thereby ploughing the field for further discovery in that business.
A funny thing about this is that "vaccination" comes from the french word "vache" which means cow. It has nothing to do with Jenners vaccinations though. The thing is that a newborne calf is very very sensitive against all infections untill it gets a drink from its mother, - it must be the first milk and within a few hours from birth. The first milk contains material to make the resistance system of the calf work, - hence the calf gets a big "vaccination"
So, we all owe something to this Frenchman named Lois Pasteur
