herd immunity
noun
: a reduction in the risk of infection with a specific communicable disease (such as measles or influenza) that occurs when a significant proportion of the population has become immune to infection (as because of previous exposure or vaccination) so that susceptible individuals are much less likely to come in contact with infected individuals
… when the percentage of people vaccinated against a particular disease drops, herd immunity begins to fail.—
Katherine Hobson
Katherine HobsonSerious streptococcal disease does seem to be on the rise, however, perhaps because invasive strains are circulating against which we have not had time to develop much "herd immunity," as epidemiologists say.—Wayne Biddle
Wayne BiddleExamples of herd immunity in a Sentence
Recent Examples on the Web
The World Health Organization considers 95% the necessary threshold to maintain herd immunity.
—Patrick Smith, NBC News, 25 Jan. 2024
Measles was officially declared eradicated in the U.S. more than 20 years ago, but new outbreaks of the disease are popping up — and experts say declining vaccination rates are jeopardizing herd immunity and increasing the risk.
—Stephen Stock, Leigh Ann Winick, CBS News, 23 Jan. 2024
The World Health Organization says there needs to be at least 95% of vaccination in a population for herd immunity.
—Michelle Marchante, Miami Herald, 27 Feb. 2024
That is below the 95% vaccination threshold health experts say is needed for herd immunity against measles.
—Michelle Marchante, Miami Herald, 22 Feb. 2024
The World Health Organization considers 95% the threshold necessary for herd immunity from measles.
—Katie Mogg, NBC News, 20 Feb. 2024
Last school year, that dropped to 92.8% — below the 95% needed for herd immunity.
—Stephen Stock, Leigh Ann Winick, CBS News, 23 Jan. 2024
Another state, Louisiana, joined the suit along with three doctors who co-signed a paper on herd immunity, an anti-lockdown activist in Louisiana, and a conservative news site, The Gateway Pundit.
—Sarah Owermohle, STAT, 6 Feb. 2024
The share of schools below herd immunity has fallen from 50% to 20%, and exemptions have fallen to less than 2%.
—Stephen Stock, Aparna Zalani, Chris Hacker, CBS News, 30 Jan. 2024
Patrick Smith, NBC News, 25 Jan. 2024
Measles was officially declared eradicated in the U.S. more than 20 years ago, but new outbreaks of the disease are popping up — and experts say declining vaccination rates are jeopardizing herd immunity and increasing the risk.
—Stephen Stock, Leigh Ann Winick, CBS News, 23 Jan. 2024
The World Health Organization says there needs to be at least 95% of vaccination in a population for herd immunity.
—Michelle Marchante, Miami Herald, 27 Feb. 2024
That is below the 95% vaccination threshold health experts say is needed for herd immunity against measles.
—Michelle Marchante, Miami Herald, 22 Feb. 2024
The World Health Organization considers 95% the threshold necessary for herd immunity from measles.
—Katie Mogg, NBC News, 20 Feb. 2024
Last school year, that dropped to 92.8% — below the 95% needed for herd immunity.
—Stephen Stock, Leigh Ann Winick, CBS News, 23 Jan. 2024
Another state, Louisiana, joined the suit along with three doctors who co-signed a paper on herd immunity, an anti-lockdown activist in Louisiana, and a conservative news site, The Gateway Pundit.
—Sarah Owermohle, STAT, 6 Feb. 2024
The share of schools below herd immunity has fallen from 50% to 20%, and exemptions have fallen to less than 2%.
—Stephen Stock, Aparna Zalani, Chris Hacker, CBS News, 30 Jan. 2024
These examples are programmatically compiled from various online sources to illustrate current usage of the word 'herd immunity.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.
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Cite this Entry
“Herd immunity.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/herd%20immunity. Accessed 1 May. 2024.
Copy CitationMedical Definition
herd immunity
noun
: a reduction in the probability of infection that is held to apply to susceptible members of a population in which a significant proportion of the individuals are immune because the chance of coming in contact with an infected individual is less
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