Variolation

Variolation or inoculation was the method first used to immunize an individual against smallpox (Variola) with material taken from a patient or a recently variolated individual in the hope that a mild, but protective infection would result. 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 patient would develop pustules identical to those caused by naturally occurring smallpox, usually producing a less severe disease than 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 and the Middle East before it was introduced into England and North America in the 1720s in the face of some opposition. The method is no longer used today. It was replaced by smallpox vaccine, a safer alternative. This in turn led to the development of the many vaccines now available against other diseases.

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 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 is used synonymously with injection in connection with the use of vaccines or other biopharmaceuticals, but has other meanings in e.g. laboratory work.

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