vaccine

American  

[vak-seen, vak-seen, -sin] / vækˈsin, ˈvæk sin, -sɪn /

noun

1. 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.

2. (no longer in technical use) the virus of cowpox, used in vaccination, obtained from pox vesicles of a cow or person.

3. a software program that helps to protect against computer viruses, as by detecting them and warning the user.

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adjective

1. of or relating to vaccination.

2. of or relating to vaccinia.

3. of, relating to, or derived from cows.

vaccine British  

/ ˈvæksiːn /

noun

1. 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

2. (originally) a preparation of the virus of cowpox taken from infected cows and inoculated in humans to produce immunity to smallpox

3. (modifier) of or relating to vaccination or vaccinia

4. computing a piece of software designed to detect and remove computer viruses from a system

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vaccine Scientific  

/ văk-sēn′ /

1. 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.

2. See Note at Jenner

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vaccine Cultural  

1. 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.

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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

Explanation

To prevent you from getting sick, a doctor will give you a shot with a vaccine in it, which is a mixture that teaches your body how to fight against viruses and diseases. It’s fascinating how vaccines work. A dead or really weak strain of a virus is injected into your body, and your system creates antibodies specifically designed to fight that particular virus. Once your body learns how to make those antibodies, you become immune to the virus, and it can’t make you sick. The word comes from the Latin vacca, meaning “cow,” because in 1796 a doctor used “cow pox” viruses to create a vaccine to prevent smallpox. Thank you, cows.

Example Sentences

The measles-mumps-rubella vaccine is the most effective protection from measles, according to the public health department.

From Los Angeles Times • May 17, 2026

“The MMR vaccine is the safest and most reliable way to prevent measles and protect yourself, your family, and your community.”

From Los Angeles Times • May 17, 2026

An Ebola outbreak in the Democratic Republic of Congo that has caused at least 80 deaths has a "very high lethality rate" and no vaccine or specific treatment, the country's health minister warned Saturday.

From Barron's • May 16, 2026

However, research suggests the MenB vaccine doesn't necessarily prevent transmission of the infection from person to person, doesn't target all the different B bacteria strains and doesn't provide very long-term protection.

From BBC • May 15, 2026

I think of Mr. Gideon's vaccine for a moment, but there’s no way that thing works.

From "Dread Nation" by Justina Ireland

Related Words

• antibiotic
• cure
• drug
• medication
• pharmaceutical
• pill
• prescription
• remedy