[ vak-seen or, especially British, vak-seen, -sin ]
/ vækˈsin or, especially British, ˈvæk sin, -sɪn /


any preparation used as a preventive inoculation to confer immunity against a specific disease, usually employing an innocuous form of the disease agent, as killed or weakened bacteria or viruses, to stimulate antibody production.
the virus of cowpox, used in vaccination, obtained from pox vesicles of a cow or person.
a software program that helps to protect against computer viruses, as by detecting them and warning the user.


of or relating to vaccination.
of or relating to vaccinia.
of, relating to, or derived from cows.



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Origin of vaccine

<New Latin (variolae) vaccīnae cowpox (in title of E. Jenner's treatise of 1798), equivalent to vacc(a) cow + -īnae, feminine plural of -īnus-ine1


pro·vac·cine, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2021

British Dictionary definitions for vaccine

/ (ˈvæksiːn) /

noun med

a suspension of dead, attenuated, or otherwise modified microorganisms (viruses, bacteria, or rickettsiae) for inoculation to produce immunity to a disease by stimulating the production of antibodies
(originally) a preparation of the virus of cowpox taken from infected cows and inoculated in humans to produce immunity to smallpox
(modifier) of or relating to vaccination or vaccinia
computing a piece of software designed to detect and remove computer viruses from a system

Word Origin for vaccine

C18: from New Latin variolae vaccīnae cowpox, title of medical treatise (1798) by Edward Jenner, from Latin vacca a cow
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medical definitions for vaccine

[ văk-sēn văksēn′ ]


A preparation of a weakened or killed pathogen, such as a bacterium or virus, or of a portion of the pathogen's structure that upon administration stimulates antibody production against the pathogen but is incapable of causing severe infection.
A vaccine prepared from the cowpox virus and inoculated against smallpox.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Scientific definitions for vaccine

[ văk-sēn ]

A preparation of a weakened or killed pathogen, such as a bacterium or virus, or of a portion of the pathogen's structure, that stimulates immune cells to recognize and attack it, especially through antibody production. Most vaccines are given orally or by intramuscular or subcutaneous injection. See Note at Jenner.

A Closer Look

In the 1950s, polio epidemics left thousands of children with permanent physical disabilities. Today, infants are given a vaccine to prevent infection with the polio virus. That vaccine, like most others, works by stimulating the body's immune system to produce antibodies that destroy pathogens. Scientists usually prepare vaccines by taking a sample of the pathogen and destroying or weakening it with heat or chemicals. The inactivated or attenuated pathogen loses its ability to cause serious illness but is still able to stimulate antibody production, thereby conferring immunity. The Salk polio vaccine contains “killed” virus, while the Sabin polio vaccine contains weakened “live” poliovirus. (Many scientists no longer consider viruses to be living organisms) Scientists are also able to change the structure of viruses and bacteria at the molecular level, altering DNA so that the potential of the vaccine to cause disease is decreased. New vaccines containing harmless bits of DNA have also been developed.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for vaccine

[ (vak-seen) ]

A substance prepared from dead or living microorganisms that is introduced into the body through inoculation. The vaccine causes the development of antibodies, which produce immunity to the disease caused by the microorganism.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.