From the earliest eras of history, healers observed that if a person happened to survive a given illness the first time, he or she would not become ill if exposed to the same illness in the future. Specifically, people who contracted and then survived smallpox (variola) would not suffer the infection the next time a smallpox epidemic swept through the community. This concept led to the process of variolation, where scabs or pus from a person infected with smallpox would be introduced into another person. The hope was that this exposure would only induce a mild case of smallpox in the recipient and thus protect the recipient from a severe case of smallpox in the future.
There were several recorded methods of variolation. The first was to remove scabs from a person infected with smallpox, let them dry, and then grind them into a powder. That powder could either be inhaled by an uninfected person or introduced into the recipient’s vein using a needle. Another method involved removing some pus and fluid from a smallpox blister and placing it under the skin of the recipient.
The origin of variolation is unclear, with different accounts stating that it occurred in China as early as 200 BC, AD 1100, and AD 1579. Whenever it began, variolation had progressed and spread across Asia in time to be common practice in the Ottoman Empire in 1716. It was in that year that the wife of the British ambassador, Lady Mary Wortley Montagu, observed physicians in Constantinople performing the procedure. She was sufficiently impressed to allow her own son to be inoculated.
After she returned to England in 1721, Lady Montagu had her daughter successfully inoculated against smallpox. This procedure caught the attention of the royal physician, and an experiment was planned. Several prisoners who were sentenced to death were offered the opportunity for freedom in exchange for undergoing variolation. All the prisoners survived. Within several years, the royal family of Britain and the royal families of many other countries underwent the procedure.
Variolation was never completely safe. While many recipients only had a mild case of smallpox, it was possible to develop a more severe case as well. Reports show that 1–2 percent of recipients actually died after the procedure. However, when compared to a mortality rate of 30 percent during a smallpox epidemic, it was felt to be a risk worth taking.