In the 17th century, physicians in Europe became aware of this.
Lady Mary Wortley Montagu was a prominent member of society, noted beauty and the wife of the British Ambassador to the Ottoman Empire. In 1715, she contracted smallpox & suffered severe facial scarring and loss of her eyelashes (!)
In 1718, while living in Turkey, she had her 6 year old son variolated, despite the violent opposition of the British Embassy staff in Constantinople. This act did much to publicize the practice of variolation after her return to Britian.
In 1721, a smallpox epidemic broke out in Britian and Lady Mary was instrumental in getting several children of the aristocracy variolated, which came to the attention of the College of Physicians.
At the same time in colonial America, trials of variolation were being carried out in Boston by the Reverend Cotton Mather.
However, as in Britian, these experiments met with disapproval from the heirachy of the medical profession, but nevertheless continued.