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The Veterinary Clinics of North... Nov 2019Herd immunity is an important concept of epidemic theory regarding the population-level effect of individual immunity to prevent transmission of pathogens. Herd immunity... (Review)
Review
Herd immunity is an important concept of epidemic theory regarding the population-level effect of individual immunity to prevent transmission of pathogens. Herd immunity exists when sufficient numbers of animals in a group or population have immunity against an agent such that the likelihood of an effective contact between diseased and susceptible individuals is reduced. Understanding herd immunity requires consideration of infection dynamics, modes of transmission, as well as the acquisition of immunity by individuals in the population. Loss of herd immunity may also explain age-associated epidemics of disease related to loss of passively acquired maternal immunity.
Topics: Animals; Epidemics; Humans; Immunity, Herd; Vaccination
PubMed: 31590904
DOI: 10.1016/j.cvfa.2019.07.001 -
Current Biology : CB Feb 2021Herd immunity is an important yet often misunderstood concept in epidemiology. As immunity accumulates in a population - naturally during the course of an epidemic or...
Herd immunity is an important yet often misunderstood concept in epidemiology. As immunity accumulates in a population - naturally during the course of an epidemic or through vaccination - the spread of an infectious disease is limited by the depletion of susceptible hosts. If a sufficient proportion of the population is immune - above the 'herd immunity threshold' - then transmission generally cannot be sustained. Maintaining herd immunity is therefore critical to long-term disease control. In this primer, we discuss the concept of herd immunity from first principles, clarify common misconceptions, and consider the implications for disease control.
Topics: Animals; Communicable Disease Control; Epidemics; Humans; Immunity, Herd; Mice; Vaccination
PubMed: 33621500
DOI: 10.1016/j.cub.2021.01.006 -
Recent Patents on Biotechnology Aug 2022The severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) has spread exponentially, leading to an alarming number of deaths worldwide. A devastating... (Review)
Review
The severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) has spread exponentially, leading to an alarming number of deaths worldwide. A devastating effect has been observed in susceptible populations. Our body's immune system plays a very important role in fighting against diseases. The principle of herd immunity (also known as population immunity), which has found its way into science and has been in the limelight, is the most widely recognised among all. It is an indirect defence against infectious diseases when a community gained immunity, either through vaccines or through prior infection. Herd immunity against COVID-19 must be achieved to reduce the transmission of disease and save lives. Therefore, this review provides a comprehension of the role of immunity, with a special emphasis on herd immunity against COVID-19, and the ways to attain herd immunity in India have also been discussed.
Topics: COVID-19; Humans; Immunity, Herd; India; Patents as Topic; SARS-CoV-2
PubMed: 35400332
DOI: 10.2174/1872208316666220408113002 -
American Journal of Clinical Pathology Mar 2021
Topics: COVID-19; COVID-19 Vaccines; Global Health; Humans; Immunity, Herd
PubMed: 33399182
DOI: 10.1093/ajcp/aqaa272 -
Global Health Research and Policy Dec 2021The World Health Organization described herd immunity, also known as population immunity, as the indirect fortification from an infectious disease that happens when a... (Review)
Review
The World Health Organization described herd immunity, also known as population immunity, as the indirect fortification from an infectious disease that happens when a population is immune either through vaccination or immunity developed through previous exposure to infection. The emergence of COVID-19 vaccine is a step towards the achievement of herd immunity. Over one billion people across the globe have been vaccinated and Africa recorded only 2%. The objective of this article was to develop a forecast of the number of people to be vaccinated to achieve herd immunity in the 13 WHO-identified priority African countries for COVID-19. Herd immunity is achieved when one infected person in a population causes less than one secondary case on average, corresponding to the effective basic reproduction number (R). Vaccine delivery and distribution infrastructure including the cold chain remains weak. Vaccine hesitancy is also one of the limiting factors that may hinder herd immunity in Africa. In order to achieve herd immunity globally, African countries should not be excluded in fair and equal distribution of vaccines. Relevant stakeholders should foster commitment as well as community sensitization on COVID-19 vaccines and integration of COVID-19 vaccines in existing healthcare services.
Topics: Africa; COVID-19; COVID-19 Vaccines; Humans; Immunity, Herd; SARS-CoV-2; Vaccination Hesitancy
PubMed: 34852844
DOI: 10.1186/s41256-021-00231-1 -
Physical Biology Jun 2021A population can be immune to epidemics even if not all of its individual members are immune to the disease, so long as sufficiently many are immune-this is the... (Review)
Review
A population can be immune to epidemics even if not all of its individual members are immune to the disease, so long as sufficiently many are immune-this is the traditional notion of herd immunity. In the smartphone era a population can be immune to epidemics-a notion we call 'digital herd immunity', which is similarly an emergent characteristic of the population. This immunity arises because contact-tracing protocols based on smartphone capabilities can lead to highly efficient quarantining of infected population members and thus the extinguishing of nascent epidemics. When the disease characteristics are favorable and smartphone usage is high enough, the population is in this immune phase. As usage decreases there is a novel 'contact-tracing phase transition' to an epidemic phase. We present and study a simple branching-process model for COVID-19 and show that digital immunity is possible regardless of the proportion of non-symptomatic transmission.
Topics: COVID-19; Communicable Disease Control; Contact Tracing; Humans; Immunity, Herd; Mobile Applications; Models, Biological; SARS-CoV-2; Smartphone; Systems Analysis
PubMed: 33827059
DOI: 10.1088/1478-3975/abf5b4 -
Lancet (London, England) Nov 2020
Topics: Confusion; Humans; Immunity, Herd; Vaccination
PubMed: 33228920
DOI: 10.1016/S0140-6736(20)32167-X -
Current Opinion in Virology Feb 2020We review and contrast the evidence for an effect of amplifying host herd immunity on circulation and human exposure to arboviruses. Herd immunity of short-lived West... (Review)
Review
We review and contrast the evidence for an effect of amplifying host herd immunity on circulation and human exposure to arboviruses. Herd immunity of short-lived West Nile virus avian amplifying hosts appears to play a limited role in levels of enzootic circulation and spillover infections of humans, which are not amplifiers. In contrast, herd immunity of nonhuman primate hosts for enzootic Zika, dengue, and chikungunya viruses is much stronger and appears to regulate to a large extent the periodicity of sylvatic amplification in Africa. Following the recent Zika and chikungunya pandemics, human herd immunity in the Americas quickly rose to ∼50% in many regions, although seroprevalence remains patchy. Modeling from decades of chikungunya circulation in Asia suggests that this level of herd immunity will suppress for many years major chikungunya and Zika epidemics in the Americas, followed by smaller outbreaks as herd immunity cycles with a periodicity of up to several decades.
Topics: Animals; Arbovirus Infections; Arboviruses; Humans; Immunity, Herd
PubMed: 32193135
DOI: 10.1016/j.coviro.2020.02.004 -
American Journal of Health Promotion :... Jul 2020
Topics: Humans; Immunity, Herd
PubMed: 32551934
DOI: 10.1177/0890117120930536d -
The Lancet. Respiratory Medicine Feb 2021
Topics: COVID-19; Humans; Immunity, Herd
PubMed: 33245861
DOI: 10.1016/S2213-2600(20)30555-5