Variolation

Variolation is the practice of exposing a person to pus or scabs derived from a person infected with smallpox in order to produce a weak infection. Compared to naturally acquired infections, which have a 30% fatality rate, variolation, with its 1-2% fatality rate, is a relatively safe way to acquire immunity to smallpox. Similar procedures performed for other diseases are known as inoculations, variolation is specific to smallpox as the name is derived from the variola virus, which is the causative agent of smallpox.

Knife for smallpox inoculation

Drawing of an inoculation knife from Sun Shi yi'an (Doctor Sun's Casebooks) by Sun Qishun, dated 1817

Thorns used for variolation in Palestine

Two thorns used for smallpox inoculation in Palestine, 1921

The most common method of variolation was taking pus or scabs (which were dried and powdered) from a smallpox patient and inserting that material into a cut on a healthy person to cause an infection. However, other methods were practiced as well. In Russia, some created a drink with smallpox material in it, and in China, smallpox tissue was inserted into a person's nose. Variolation was practiced for hundreds of years and in many places around the world.

Despite variolation being much safer than naturally acquired smallpox, it still killed people, and those who were variolated were still infected with smallpox. If they weren't careful, a variolated person could start an outbreak of smallpox. Due to these drawbacks and the discovery of vaccination, which is much safer and has fewer risks, variolation fell out of practice over the course of the nineteenth century.