One theory about preventing smallpox was that it had been noticed that some people who caught a milder form of smallpox, recovered and nevercaught it again.
Some tried to infectthemselves with smallpox with the idea that they would avoid catching a more severe form. This worked for some there were still deaths.
A small cut was made in the patient’s arm before dropping in pus taken from the swelling of someone with a mild form of smallpox.
Inoculation was expensive and only the rich could afford it. Some doctors made a fortune carrying out inoculations.
eg Dr. ThomasDimsdale inoculated Catherine the Great and her children in 1768. As a reward he was made a baron and paid £10,000. Being a smallpox ‘inoculator’ was very profitable!