Within the context of medicine, inoculation refers to the introduction of a substance into the body that will cause an immune response that can provide future protection against a specific disease. Today the term is used in relation to vaccination in general, but historically it was used to refer to techniques used against smallpox before the widespread acceptance of Edward Jenner’s smallpox vaccine.
Active inoculation grew from the well-observed phenomenon in which individuals who survived an often fatal infectious disease rarely contacted that disease again. The first attempts to induce such an immune response artificially are recorded in China approximately a thousand years ago. There, powder made from the crusts of smallpox scabs were deliberately inhaled. Although struck down by a milder form of the disease, the recipients of the powder usually survived with their new disease immunity intact.
Inoculation against smallpox was known specifically as variolation – variola being the Latin name for smallpox. While in the Far East and parts of Africa, the inhalation technique was often used, in other parts of the world applying powder or pus from a smallpox pustule under the surface of the skin was the preferred method. The skin was first scratched, perhaps with a sharp instrument or even a thorn, then the powder or pus was rubbed into the wound.