Smallpox vaccination is the way to prevent the disease initiated in ancient China. Smallpox was called "vaccinatable boil" in China at that time, hence the name of the prevention measure—"boil vaccination", which is done by slightly infecting someone with the disease. The person will then get immunity against smallpox after slightly suffering from it and they'll never contract the disease again. Originally, people were afraid of contracting smallpox, but they later deliberately get it for the purpose of vaccination. That was a great change, which was brought about by the experiences accumulated in the process of combating the disease.    

Chinese smallpox vaccination began to be introduced overseas in the early 17th century. First in 1688, Russia asked to send doctors to learn the skill. Later, Korea, Japan and other countries all followed suit.