At the end of the eighteenth century, English physician Edward Jenner was studying the smallpox disease and noticed that dairy farmers who had previously suffered from cowpox, a cattle-borne disease similar to smallpox but much less virulent, were resistant to smallpox infection. He therefore reasoned that healthy people might become immune to smallpox if injected with a little pus from a cowpox lesion—a supposition that turned out to be correct—and he referred to the medicinal cowpox matter as a vaccine and his method for using it to shield against smallpox as a vaccine inoculation (a phrase he soon contracted to vaccination). Jenner used the Latin adjective vaccinus, meaning “of a cow,” as the basis for vaccine, and by 1803, his new English noun and its logical derivative, the verb vaccinate, were already in wide use. It was another forty years, however, before the terms were freed from their bovine roots and used in reference to all inoculating medicines rather than just the one derived from the cowpox virus.
©2018 Michael R. Gates
