What did Jenner discover?

Developed "smallpox" method of preventing smallpox

Smallpox is one of the most frightening diseases. If infected, a person develops a high fever and a rash all over the body, and may die after suffering from it.

Smallpox is caused by a virus and is highly contagious. Once the smallpox virus is contracted, it can spread very quickly.
Jenner came up with the idea of "smallpox" as a way to prevent people from contracting this dreaded disease. This enabled people all over the world to live without worrying about smallpox.

Edward
Jenner
(Edward Jenner)
1749-1823
English, physician

The History of Man's Battle Against Smallpox Smallpox is said to be as old as 12,000 years ago and has caused countless deaths.
Many kings and other important people were involved in the disease, and if it had not been for smallpox, the history of the disease might have been different.

What kind of prophylaxis is "smallpox"?

When a virus enters the body, the body produces a substance called an antibody to try to expel it. This mechanism is called immunity, and once antibodies are formed, the body is no longer susceptible to the same disease.
Jenner developed a preventive method called "smallpox" that utilized this power. The method was to inject a person who had cowpox, which is not as dangerous as smallpox, into a person who had not yet contracted smallpox, in order to create smallpox antibodies. This is a method to create smallpox antibodies in people who have not been exposed to smallpox. In this way, everyone was spared from contracting real smallpox.

A Conversation with a Bovine Milker Gives Jenner a Hint for His Research One day, Jenner heard from a cow milker that people who had cowpox did not get smallpox.
Taking this story as a hint, Jenner began researching smallpox and repeatedly conducted experiments on cows and pigs. Finally, he completed the "smallpox" experiment, proving his hypothesis correct.

Is it true that Jenner was good at something other than medicine?

Jenner was famous not only as a physician but also as a naturalist. Natural history is the study of all things in nature, including animals, plants, minerals, and geology.
Nature observation, animal observation, and insect collecting (insect collecting) are typical natural history research methods.
Jenner observed and studied animals and plants, and collected fossils in between his studies of disease.
In addition to his research, Jenner was an accomplished violinist, and his skill at playing the violin was quite impressive.

As a naturalist, he discovered the surprising habits of the cuckoo. The cuckoo bird has a habit of laying its eggs in the nests of other birds and allowing the nest owner to raise them.
After emerging from the egg, the cuckoo chick drops all the other birds' eggs from the nest, pretends to be a child, and asks the other birds to raise it. Jenner was the first to discover this surprising behavior of the cuckoo.