Vaccinations allow a body to develop immunity to a pathogen by stimulating the immune system. A vaccine is substance that contains an agent the looks like a pathogen and is typically injected into the bloodstream.
The first lab created vaccine was by French biologist Louis Pasteur, after whom the process pasteurization is named. He was working with chicken cholera. He cultivated the bacteria in chicken broth, but found the bacteria had spoiled and didn’t induce the disease in the chickens. When he tried to inject the same chickens with fresh bacteria he found that they were immune to the disease. Pasteur also created vaccines for anthrax, swine erysipelas and rabies.
Vaccinations work by stimulating the immune system to develop antibodies without actually giving the person the disease. Vaccinations are now commonplace in many medical systems. They have hugely reduced the number of people dying of communicable diseases. Vaccinations have been responsible for the eradication of smallpox.
The first vaccine was delivered to a human was by Edward Jenner. Jenner developed this vaccine in 1796 when he noticed that milkmaids did not catch smallpox if they had been previously infected with cowpox. He injected a boy with material from an infected blister of a woman with cowpox. He later injected the boy again with smallpox, but noted he did not develop the disease. He wrote this in a paper named "An Inquiry into the Causes and Effects of the Variolae Vaccinae", which is where the term vaccine comes from. His paper was translated into many languages and thousands of people were vaccinated as a result.