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
In the 2019-2020 school year, 95% of kindergarteners had received the MMR vaccine, the target to achieve herd immunity.
—Caleb McCullough, Austin American Statesman, 2 July 2025
Research published this month by Johns Hopkins University in JAMA showed 1,600 counties around the country have vaccination rates below 91 percent, missing the 95 percent mark for herd immunity.
—Lexi Lonas Cochran, The Hill, 16 June 2025
No kindergarten classes in any of those three counties had herd immunity from measles this academic year.
—Stephanie Innes, AZCentral.com, 9 June 2025
Focused protection, the drafters wrote, would allow society to achieve herd immunity and return to normality in three to six months.
—Michael Hiltzik, Los Angeles Times, 5 June 2025
See All Example Sentences for herd immunity
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Caleb McCullough, Austin American Statesman, 2 July 2025
Research published this month by Johns Hopkins University in JAMA showed 1,600 counties around the country have vaccination rates below 91 percent, missing the 95 percent mark for herd immunity.
—Lexi Lonas Cochran, The Hill, 16 June 2025
No kindergarten classes in any of those three counties had herd immunity from measles this academic year.
—Stephanie Innes, AZCentral.com, 9 June 2025
Focused protection, the drafters wrote, would allow society to achieve herd immunity and return to normality in three to six months.
—Michael Hiltzik, Los Angeles Times, 5 June 2025
See All Example Sentences for herd immunity
Cite this Entry
“Herd immunity.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/herd%20immunity. Accessed 29 Jul. 2025.
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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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