1 Min Read How Did Pasteur Discover ‘Vaccines’?

In 1879, Louis Pasteur was studying chicken cholera — a bacterial disease that could kill chickens in large numbers within days.

In his laboratory, there was a batch of 'old' chicken cholera bacterial cultures that had been sitting for weeks without being used in experiments. After the summer holiday ended and everyone returned to the lab, Pasteur's assistant injected a batch of chickens with these old cultures.

Something strange happened: the chickens got sick, but didn't die.

Then something even stranger happened: when these chickens that had 'pulled through' were injected again with fresh, lethal doses of chicken cholera bacteria, they were fine.

Pasteur stared at this result, thought of Jenner and cowpox. Then he realized: there was a universal principle here. Weakened (attenuated) pathogens could train the immune system to fight the stronger version.

He named this principle 'vaccination' — deliberately using Jenner's word, as a tribute to that country doctor.