Ans: Variolation is a prevention method of smallpox. In England, Lady Mary Wortley Montagu invented this method to prevent smallpox. In this method, people are immunized by infecting the substances from the patients' pustules. The substances are injected under the skin. After injecting the substances into the body of the unaffected people, they are infected with a mild form of smallpox (variola minor). Thus, the people are affected less dangerously and an immune system against smallpox is built in their body. This immune system protects them from the disease in the future. In the 18th century, variolation was able to control the spread and harm of smallpox.