Physiologic Function
herd immunity
herd im·mu·ni·ty
Subclass of:
Immune response
Definitions related to immunity, herd:
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(herd immunity) Immunity (via exposure to a pathogen or via vaccination) for a majority of the individuals in a community that serves to protect a na�ve segment of that same population who cannot receive vaccination (contraindicated) and is therefore especially vulnerable to disease. The effect is described by the epidemiological principle that if immunity (via successful vaccination) was delivered at random and if members of a population mixed at random, such that on average each individual contacted R0 individuals in a manner sufficient to transmit the infection, then incidence of the infection would decline if the proportion immune exceeded (R0 - 1)/R0, or 1 -1/R0, where R0 is the basic reproductive number.NCI ThesaurusU.S. National Cancer Institute, 2021
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(herd immunity) Protection occurring when so many people in a region are immune to an infectious disease that it can't spread to others.Harvard Dictionary of Health TermsHarvard Medical Publishing, 2011
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The non-susceptibility to infection of a large group of individuals in a population. A variety of factors can be responsible for herd immunity and this gives rise to the different definitions used in the literature. Most commonly, herd immunity refers to the case when, if most of the population is immune, infection of a single individual will not cause an epidemic. Also, in such immunized populations, susceptible individuals are not likely to become infected. Herd immunity can also refer to the case when unprotected individuals fail to contract a disease because the infecting organism has been banished from the population.NLM Medical Subject HeadingsU.S. National Library of Medicine, 2021
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Herd immunity, state in which a large proportion of a population is able to repel an infectious disease, thereby limiting the extent to which the disease can spread from person to person. Herd immunity can be conferred through natural immunity, previous exposure to the disease, or vaccination. An...Encyclopedia Britannica, Inc., 2020
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