Ans: In the 18th century, variolation was the only way to prevent smallpox. At that time, variolation was able to control the spread and harm of smallpox. Variolation can protect people from smallpox to a particular extent. It is the method for preventing smallpox, not for treatment. Also, there were some problems with the procedure of variolation. In some cases, variolation was unable to protect the patient from the second attack. A permanent treatment for smallpox was necessary. British scientist Edward Jenner researched cowpox and used it against smallpox as protection. In 1796, Edward Jenner vaccinated James Phipps successfully using cowpox substances. Thus, the vaccine for smallpox was invented.