Variolation was a real practice used to combat smallpox. It involved taking pus or skin cells from a smallpox infected person and then administering it into a cut or scratch on a healthy person. The process was common in parts of Asia and Africa but was greeted by skepticism when originally introduced into Europe and European colonies in the Americas. Variolation was an effective way to give people immunity to smallpox but it did carry risks. Not mentioned in the episode is the fact that variolation actually caused the patient to develop a mild case of smallpox. This was rarely fatal, but it could incapacitate someone for a while. Importantly, while undergoing the treatment, a patient was actually contagious, and could give smallpox to uninfected people. Because of this, people undergoing variolation normally quarantined themselves, and large scale variolation efforts, such as the one George Washington carried out on the Continental Army during the American Revolution, had to be carefully managed in order to prevent outbreaks.