1831: vaccine Dec 20, 2019

In some sense, the first vaccine invented was to treat smallpox, but it was not made with strains of 'smallpox' itself. When it was discovered that once someone contracted cowpox virus, he would be immune to smallpox. The word 'vaccine' still reflects that, coming from the Latin 'vacca' meaning 'cow', though of course this is now applied to a vaccine for any illness.

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