/ ˈvæksiːn; NAmE vækˈsiːn/ noun
[ C , U ] a substance that is put into the blood and that protects the body from a disease :
a measles vaccine
There is no vaccine against HIV infection.
—picture at injection
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WORD ORIGIN
late 18th cent.: from Latin vaccinus , from vacca cow (because of the early use of the cowpox virus against smallpox).