vaccine

noun

vac·​cine vak-ˈsēn 

ˈvak-ˌsēn

plural vaccines

1

: a preparation that is administered (as by injection) to stimulate the body's immune response against a specific infectious agent or disease: such as

a

: an antigenic preparation of a typically inactivated or attenuated (see attenuated sense 2) pathogenic agent (such as a bacterium or virus) or one of its components or products (such as a protein or toxin)

a trivalent influenza vaccine

oral polio vaccine

Many vaccines are made from the virus itself, either weakened or killed, which will induce antibodies to bind and kill a live virus. Measles vaccines are just that, weakened (or attenuated) measles viruses.

—Ann Finkbeiner et al.

… a tetanus toxoid-containing vaccine might be recommended for wound management in a pregnant woman if [greater than or equal to] 5 years have elapsed … .

—Mark Sawyer et al.

In addition the subunit used in a vaccine must be carefully chosen, because not all components of a pathogen represent beneficial immunological targets.

—Thomas J. Matthews and Dani P. Bolognesi

b

: a preparation of genetic material (such as a strand of synthesized messenger RNA) that is used by the cells of the body to produce an antigenic substance (such as a fragment of virus spike protein)

… Moderna's coronavirus vaccine … works by injecting a small piece of mRNA from the coronavirus that codes for the virus' spike protein. … mRNA vaccine spurs the body to produce the spike protein internally. That, in turn, triggers an immune response.

—Susie Neilson et al.

The revolutionary messenger RNA vaccines that are now available have been over a decade in development. … Messenger RNA enters the cell cytoplasm and produces protein from the spike of the Covid-19 virus.

—Thomas F. Cozza

Viral vector vaccines, another recent type of vaccine, are similar to DNA and RNA vaccines, but the virus's genetic information is housed in an attenuated virus (unrelated to the disease-causing virus) that helps to promote host cell fusion and entry.

—Priya Kaur

Note: Vaccines may contain adjuvants (such as aluminum hydroxide) designed to enhance the strength and duration of the body's immune response.

2

: a preparation or immunotherapy that is used to stimulate the body's immune response against noninfectious substances, agents, or diseases

The U.S. Army is also testing a ricin vaccine and has reported success in mice.

—Sue Goetinck Ambrose

… many of the most promising new cancer vaccines use dendritic cells to train the immune system to recognize tumor cells.

—Patrick Barry

vaccine adjective

Examples of vaccine in a Sentence

Recent Examples on the Web

Gavi is the most prominent procurer and distributor of vaccines to children across the globe. —Joshua P. Cohen, Forbes.com, 1 July 2025

Earlier this month, Kennedy dismissed all 17 members of the CDC’s vaccine advisory committee, then replaced them with a group that includes several allies who have spread misinformation about the harms of vaccines. —Hana Kiros, The Atlantic, 28 June 2025

But where do most Americans actually stand on the childhood vaccine requirements? —Irene Wright, Miami Herald, 27 June 2025

New panel members also unanimously voted to recommend the flu vaccines for all Americans six months and older. —Adrianna Rodriguez, USA Today, 26 June 2025

Word History

Etymology

earlier, "fluid from cowpox pustules used in inoculation," noun use of vaccine "of cowpox" (in the phrases vaccine disease, vaccine matter), borrowed from New Latin vaccina (in variolae vaccinae "cowpox"), going back to Latin, feminine of vaccīnus "of or from a cow," from vacca "cow" (perhaps akin to Sanskrit vaśā "cow") + -īnus -ine entry 1; in extended sense, "preparation of organisms administered to produce immunity," in part borrowed from French vaccin, masculine derivative of vaccine "cowpox, matter from cowpox pustules," borrowed from New Latin or English

First Known Use

1880, in the meaning defined at sense 1

Phrases Containing vaccine

• anti-vaccine
• BCG vaccine
• mRNA vaccine
• Sabin vaccine
• Salk vaccine
• vaccine hesitancy
• vaccine hesitant
• vaccine passport

Rhymes for vaccine

• agin
• alkene
• allene
• ameen
• amin
• amine
• arene
• athene
• baleen
• beeline
• benzene
• between

Kids Definition

vaccine

noun

vac·​cine vak-ˈsēn 

ˈvak-ˌsēn

: a preparation of killed, weakened, or fully infectious microbes that is given (as by injection) to produce or increase immunity to a particular disease

Etymology

from Latin vaccinus (adjective) "of or from cows," from vacca "cow" — related to buckaroo, vaquero

Word Origin

Toward the end of the 18th century, Edward Jenner, an English physician, made an important discovery. He observed that dairymaids who had the disease cowpox did not get smallpox, a much more serious disease. Working from this observation, he injected a person with material taken from another person's cowpox sores. He found out that this injection protected that person against the dreaded smallpox. He reported these findings in an article in which he used the Latin translation of cowpox, variolae vaccinae. The Latin word vaccinae was formed from the adjective vaccinus meaning "of or relating to cows." This word, in turn, was based on the noun vacca, meaning "cow." The cowpox material used for injections was then called vaccine. The injection itself was called vaccination. From this noun we created the verb vaccinate and the noun vaccinator.

Medical Definition

vaccine

noun

vac·​cine vak-ˈsēn, ˈvak-ˌ 

1

: a preparation that is administered (as by injection) to stimulate the body's immune response against a specific infectious agent or disease: such as

a

: an antigenic preparation of a typically inactivated or attenuated pathogenic agent (such as a bacterium or virus) or one of its components or products (such as a protein or toxin)

a trivalent influenza vaccine

Extensive use of inactivated poliovirus vaccine (IPV) (starting in 1955) and live attenuated oral poliovirus vaccine (OPV) (beginning in 1961) led to a dramatic decrease in poliomyelitis incidence in the United States …

—Mark A. Miller et al., The Journal of the American Medical Association

… a tetanus toxoid-containing vaccine might be recommended for wound management in a pregnant woman if [greater than or equal to] 5 years have elapsed since the previous Td booster.

—Mark Sawyer et al., Morbidity and Mortality Weekly Report

Many vaccines are made from the virus itself, either weakened or killed, which will induce antibodies to bind and kill a live virus. Measles vaccines are just that, weakened (or attenuated) measles viruses.

—Ann Finkbeiner, et al., John Hopkins Magazine

b

: a preparation of genetic material (such as a strand of synthesized messenger RNA) that is used by the cells of the body to produce an antigenic substance (such as a fragment of virus spike protein)

a COVID-19 vaccine

The Pfizer and Moderna vaccines are messenger RNA vaccines. They contain the genetic code for making the spike protein that the SARS-CoV-2 virus uses to latch onto and invade cells. Once injected, a person's cells read the code and then produce the protein.

—Sharon Kirkey, The Star Phoenix (Saskatchewan, Canada)

For an mRNA vaccine, the genetic message encoding for the protein antigen needs to be effectively delivered into the cells.

—Angus Liu, FiercePharma

Viral vector vaccines, another recent type of vaccine, are similar to DNA and RNA vaccines, but the virus's genetic information is housed in an attenuated virus (unrelated to the disease-causing virus) that helps to promote host cell fusion and entry.

—Priya Kaur, Addison County (Vermont) Independent

Note: Vaccines may contain adjuvants (such as aluminum hydroxide) designed to enhance the strength and duration of the body's immune response.

2

: a preparation or immunotherapy that is used to stimulate the body's immune response against noninfectious substances, agents, or diseases

The investigational ricin vaccine, RiVax …, was effective in creating ricin-neutralizing antibodies in one of five participants given a low dose of the vaccine, four of five given an intermediate dose, and five of five receiving a high dose.

—Amy Pfeiffer, Clinical Neurology News

Dendritic cells play a key role in activating an immune response—whether against a foreign microbe or a damaged body cell—so many of the most promising new cancer vaccines use dendritic cells to train the immune system to recognize tumor cells.

—Patrick Barry, Science News

… these antigen-based cancer vaccines require gene transfer. They work best when administered to cells that are readily accessed by the immune system.

—R. Michael Blaese, Scientific American