vaccine
Americannoun
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any preventive preparation used to stimulate the body’s immune response against a specific disease, using either messenger RNA or killed or weakened bacteria or viruses to prepare the body to recognize a disease and produce antibodies.
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(no longer in technical use) the virus of cowpox, used in vaccination, obtained from pox vesicles of a cow or person.
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a software program that helps to protect against computer viruses, as by detecting them and warning the user.
adjective
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of or relating to vaccination.
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of or relating to vaccinia.
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of, relating to, or derived from cows.
noun
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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
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(originally) a preparation of the virus of cowpox taken from infected cows and inoculated in humans to produce immunity to smallpox
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(modifier) of or relating to vaccination or vaccinia
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computing a piece of software designed to detect and remove computer viruses from a system
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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.
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See Note at Jenner
Usage
What does vaccine mean? A vaccine is a substance introduced into someone’s body to prevent them from getting a specific disease. It usually consists of a small amount of a killed, weakened, or otherwise modified version of a disease (such as a virus or bacterium).Vaccines work by allowing your immune system to develop defenses against that disease, called antibodies, so they can destroy it if it ever enters your body again.Common vaccines include ones for strains of the flu, polio, hepatitis A, hepatitis B, tetanus, diphtheria, whooping cough, chickenpox, measles, mumps, and rubella. There are many others.Example: The polio vaccine has saved millions of people.
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.
Other Word Forms
- provaccine adjective
Etymology
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 -ine 1
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Helen and Lee said they feared "another outbreak like Kent could happen again" if the MenB vaccine was not made available to 15-24-year-olds on the NHS.
From BBC • Apr. 3, 2026
Could a patient sue a doctor who counsels against the measles vaccine in the midst of an outbreak?
From Slate • Mar. 31, 2026
"AI transforms a 'needle-in-a-haystack' search into a data-driven selection process, drastically shortening the timeframe between diagnosis and vaccine construction," he said.
From Barron's • Mar. 30, 2026
Pharmaceutical giant Pfizer and French vaccine maker Valneva reported positive topline results from their phase three study of a vaccine candidate for Lyme disease.
From The Wall Street Journal • Mar. 27, 2026
But they don’t never explain more than just sayin, Yeah, your mother was on the moon, she been in nuclear bombs and made that polio vaccine.
From "The Immortal Life of Henrietta Lacks" by Rebecca Skloot
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
