11 Scientific Discoveries That Were Total Accidents

3. Vaccinations

Louis Pasteur, the guy who invented and gave his name to pasteurisation, wasn't satisfied with making our milk safe to drink and turned his attention to protecting us from deadly diseases.

In the mid-1800s, he was experimenting with chicken cholera, trying to come up with a cure for the disease in humans (either that or he just really liked chickens). The experiments involved infecting the chickens on purpose and trying various methods to cure them.

During his experiments, Pasteur decided to go on holiday, leaving the responsibility of infecting his chickens to his assistant. Unfortunately, his assistant also decided to go on holiday and left a culture of chicken cholera to spoil. The dead cholera was then injected into the chickens by mistake when he got back.

Because the chickens didn't end up developing full blown cholera, Pasteur reused them, but he found that he was now unable to infect them. They had become immune to cholera.

The principle of infecting people with cowpox to prevent smallpox has already been discovered by a man called Edward Jenner, but Pasteur's discovery was the first time someone had used a weakened form of the same disease to prevent the disease. 

Good old Louis Pasteur named his discovery "vaccines" in honour of Jenner, as Jenner had used a strain of cowpox called "Vaccinia" in his experiments.

Good form all round.