Introduced into Britain from Turkey by Lady Mary Wortley Montagu in 1780, it involved making a cut in a patient's arm and soaking it in pus taken from the swelling of somebody who already had a mild form of smallpox
He was a country doctor in Gloucestershire who heard that milkmaids didn't get smallpox but they did catch the milder cow pox
In 1796, he tested his theory by injecting a small boy called James Phillips with pus from the sores of Sarah Nelms, a milkmaid with cow pox, and then infecting him with smallpox, finding that James didn't catch the disease
He published his findings in 1798 and coined the term 'vaccination' using the Latin word for cow 'vaca'