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Variolation

Former method of smallpox immunisation

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Queens of Mysore (detail), Thomas Hickey, 1805
Thomas Hickey, 1805 · Public domain

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Through Immunization, Infection and Vaccine

The procedure was most commonly carried out by inserting/rubbing powdered smallpox scabs or fluid from pustules into superficial scratches made in the skin. The virus was normally spread through the air, infecting first the mouth, nose, or respiratory tract, before spreading throughout the body via the lymphatic system. In contrast, infection of the skin usually led to a milder, localized infection, but, crucially, still induced immunity to the virus. The patient would develop pustules like those caused by naturally acquired smallpox. Eventually, after about two to four weeks, these symptoms would subside, indicating successful recovery and immunity.

The method was first used in China, India, parts of Africa and the Middle East before it was introduced into England and North America in the 1720s in the face of some opposition. However, inoculation had been reported in Wales since the early 17th century.

Terminology

The terminology used to describe the prevention of smallpox can cause confusion. In 18th-century medical terminology, inoculation refers to smallpox inoculation. Confusion is caused by writers who interchange variolation and vaccination through either mistranslation or misinterpretation. The term variolation refers solely to inoculation with smallpox virus and is related to but not interchangeable with vaccination. The latter term was first used in 1800 soon after Edward Jenner introduced smallpox vaccine derived from cowpox, an animal disease distinct from smallpox. The term variolation was then used from the 19th century to avoid confusion with vaccination. Most modern writers tend to refer to smallpox inoculation as variolation throughout without regard for chronology, as is used here. Further confusion was caused when, in 1891, Louis Pasteur honoured Jenner by widening the terms vaccine/vaccination to refer to the artificial induction of immunity against any infectious disease. Inoculation refers to intentionally exposing an individual to a virus, bacterium, other pathogen, or artificial vaccine that may induce active immunity, and inoculation can be done by any suitable route of administration. Many familiar vaccines are injected intramuscularly or swallowed.

The term "inoculation" entered medical English through horticultural usage meaning to graft a bud (or eye) from one plant into another. It is derived from the Latin in + oculus (eye).

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