Take fifteenth-century China, when healers first realized they could inoculate people against smallpox. After centuries of experimentation, they found a pattern that they could exploit to reduce the risk of death from this illness by a factor of ten. All they had to do was find an individual with a mild case of the disease, harvest their scabs, dry them, crush them and blow them into the nose of a healthy person.
Evidence exists that primitive vaccinations for the bovine form small pox existed in Anatolia (Letters from Istanbul, Lady Montegue, the wife of the British Ambassador)
