My understanding of historical response to smallpox (going from memory, so please research for yourself) was one of two methods.

1. Get cowpox (a milder infection that did not leave as significant damage or blistering to the skin and generally didn't cause death) which conveyed strong immunity to smallpox. It was common for milkmaids to get cowpox, and uncommon for them to suffer smallpox.

2. Get an inoculation to smallpox. Retrieve from a smallpox infected person pus from one of the blisters by slicing the blister and scraping a previously sterilized tool over the open wound. Cut a shallow incision into the arm of the person being inoculated. Introduce the scraped off pus material into the wound to inoculate the individual.

#1 was generally effective.

#2 supposedly introduced weakened or near dead smallpox into the person being inoculated. This method did not always work out and some still died from smallpox introduced by the inoculation. John Adams family had an inoculation of this method done and I believe the results were mixed for his family.