Biological Sciences
Herd Immunity
Herd immunity refers to the indirect protection from infectious diseases that occurs when a large percentage of a population becomes immune, either through vaccination or previous infections. When enough individuals are immune, the spread of the disease is slowed, providing protection to those who are not immune, such as individuals who cannot be vaccinated for medical reasons.
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8 Key excerpts on "Herd Immunity"
eBook - ePub- Jean-Marc Sabatier(Author)
- 2021(Publication Date)
- Bentham Science Publishers(Publisher)
44 ].Herd Immunity has reduced the frequency of many diseases, if not eliminate them. Use of meningococcal sero group C conjugate (MCC) vaccines developed Herd Immunity and reduced the number of cases significantly in unimmunized individuals [45 ]. Similarly, oral cholera vaccines quickly protect a population for a period of time. However, the protection depends on vaccine efficacy, vaccine coverage, and the rate of mobility of the population [46 ]. In Scotland, a national human papillomavirus (HPV) immunization program significantly lowered the HPV infection among nonvaccinated women within 5 years’ time from 2008 to 2013 [47 ]. India is doing a mass vaccination campaign to control and eventually eradicate foot-and-mouth disease (FMD) [48 ].PRINCIPLE OF Herd Immunity
The principle underlying Herd Immunity is that the presence of enough persons in a community immune to the disease interrupts the transmission of the disease, thereby providing indirect protection to susceptible or un-immunized individuals [49 - 52 ]. There will be a reduced probability of an un-immunized individual becoming infected when he is part of an immunized or vaccinated population (Fig.). This can be explained by a term called Herd Immunity threshold (HIT). It represents a certain percentage of population who, when become immune to a certain disease, can eliminate that disease from the population [53 ]. It is not necessary that 100% of a population need to become immune to eradicate a disease. HIT varies from disease to disease and is given in Table 1 . It may vary from 40% (for H1N1) to 94% (for measles) [54 - 562
eBook - ePub- Abner Louis Notkins(Author)
- 2014(Publication Date)
- Academic Press(Publisher)
The case was in a 3-child family and a 5-child play group and did not attend nursery school although his 2 siblings were among the 40 susceptibles who did attend. Herd Immunity is an integral part of epidemic theory, as it applies to agents which spread by relatively direct means from host to host and induce significant post-infection immunity. Epidemics arise when such agents are introduced into populations containing susceptible individuals, who make sufficient contact with one another to permit transfer of infection from each newly infected host (new case) to, on the average, more than one susceptible host. The epidemic curve declines when, on the average, each new case infects less than one susceptible and the outbreak terminates as the probability of transmission from a new case approaches zero, typically well before the supply of susceptibles has been exhausted. In real life, the reasons for decline of transmission and termination of outbreaks are multiple and include seasonal changes in environmental factors (humidity and temperature) affecting agent viability outside the host and in host behavior (outdoor play versus indoor school) influencing the opportunity for effective contact between children, as well as progressive replacement of susceptibles with immunes which generates the “Herd Immunity” effect. Popular understanding of Herd Immunity is essentially as described in a medical dictionary (4): Herd Immunity is “the resistance of a group to attack by a disease to which a large proportion of the members are immune, thus lessening the likelihood of a patient with a disease coming into contact with a susceptible individual”. This definition implies that, if a large enough proportion of the population is immune, the agent can not be transmitted and the remaining susceptibles will be protected
- Mark Davis(Author)
- 2022(Publication Date)
- Routledge(Publisher)
Affective immunity also appears to be salient for the personal experience narratives of members of the general public. In research with colleagues on pandemic influenza (Davis and Lohm, 2020) and antimicrobial resistance (Davis et al., 2020a; Davis et al., 2020b), interview participants often made reference to their immune systems as part of their healthcare approaches. In relation to pandemic influenza, interviewees recognised the value of social distancing, hygiene and vaccines, but they also believed that influenza was easy to catch and for that reason, focussed on bolstering their own immune systems. They were in effect forced into their corporeality to manage the risks of pandemic influenza, as a practical solution to infection risk were none else yet existed, but also as the basis for shoring up a safer sense of being-in-the-world with pandemic threat. Searching online for immunity webpages during the COVID-19 pandemic might be driven by similar pragmatic and affective factors. In relation to superbugs, general publics explained the gradual emergence of antimicrobial resistance through a range of concepts including the notion that their bodies had come to resist antibiotics, much like habituation to caffeine and alcohol (Erblich, 2019). These narratives also foregrounded a resort to the body’s immune system and its management in the context of health risks and how to respond to them. These beliefs about immunity and how they shape practices of everyday health care will be considered in the next chapter in further detail.Herd Immunity, immunity passports and coronavirus
Digital media, then, foreground the affective values of immunity. The content of my Google search, however, indicated that resolution of the needs and desires of Google searchers could be complicated by further challenges and uncertainties. More specifically, the news media and magazine items I collected in my Google search were all devoted to the scientific and political challenges raised by the COVID-19 pandemic. At that point in the pandemic – mid-April 2020 – the articles addressed the evolving public health response to the pandemic through two concepts: Herd Immunity and immunity passports. These materials provide important insights into the ways in which immunity is framed in digital media.Herd Immunity is a key concept from vaccination science that travels in media and came to the fore in 2020 in relation to COVID-19. There are several ways of defining Herd Immunity, but in general it refers to the proportion of a population that is immune to a virus because they have been exposed to it previously or vaccinated (Fine et al., 2011). Depending on the characteristics of a particular virus, if the proportion of immune individuals in a population is sufficiently high, the pathogen will be unlikely to find a suitable host and therefore be less often transmitted and possibly eradicated. For COVID-19, Herd Immunity was controversial because to achieve it in the absence of a vaccine meant that a significant number of individuals would face major illness and death (Hunter, 2020).
eBook - PDF- Sarah Boslaugh, Sarah E. Boslaugh(Authors)
- 2007(Publication Date)
- SAGE Publications, Inc(Publisher)
This means that if there is 1069 random mixing of individuals within the population then the pathogen cannot be spread through the population. Herd Immunity acts by breaking the trans-mission of infection or lessening the chances of susceptible individuals coming in contact with a per-son who is infectious. Herd Immunity is important because it provides a measure of protection to indivi-duals who are not personally immune to the disease— for instance, individuals who could not receive vac-cines due to age or underlying medical conditions or individuals who received vaccines but remain suscep-tible. It is Herd Immunity that made the smallpox eradication campaign possible, and it is herd immu-nity that prevents the spread of diseases such as polio and measles today. In spite of these benefits to individuals and populations, vaccination itself is not without risk. Common reactions to vaccines include redness and soreness around the vaccination site. More severe adverse reactions are also possible for some vacci-nates; these include vomiting, high fevers, seizures, brain damage, and even death, although such reac-tions are fairly rare. The most serious adverse reac-tions, for example, occur in less than one case out of a million for most vaccines. In addition to these known adverse effects of vac-cination, claims have also been made that vaccination is responsible for adverse health conditions, such as autism, speech disorders, and heart conditions. While none of these claims is well accepted in the scientific community, they have had a significant impact on individuals’ perceptions about the safety of vaccines. Combined with the fact that most individuals have never personally experienced, or seen someone expe-rience, many of the vaccine-preventable diseases in their lifetime, the focus of concern for many people has shifted from the negative effects of the diseases to the possible negative effects of the vaccines them-selves.
eBook - PDFCoronavirus Disease 2019 (Covid-19)
A Clinical Guide
- Ali Gholamrezanezhad, Michael P. Dube(Authors)
- 2022(Publication Date)
- Wiley-Blackwell(Publisher)
Using a protective lipid nanoparticle coating, these particles are taken up by cells, processed, coded for synthesis of spike protein, and presented to the immune system, triggering a humoral and a cellular immune response. The Pfizer- BioNTech and Moderna vaccines are examples of this technology and are the main vaccines used by the United States and many countries throughout Europe. These vaccines were approved by the US Food and Drug Administration for Emergency Use Authorization on 11 December 2020 for Pfizer and on 18 December 2020 for Moderna [60, 63]. The Pfizer vaccine received full US Food and Drug Administration approval on 23 August 2021. The goals of vaccination are grounded on two key concepts: bolstering individual immunity to prevent severe disease and hospitalization and to limit population-wide spread. “Herd Immunity” is an indi- rect form of protection resulting from enough individ- uals obtaining immunity, via vaccination or infection, to the point where it minimizes further disease circu- lation within a population. This threshold varies from pathogen to pathogen. Herd Immunity to SARS- CoV-2 has been estimated, giving circulating strain considerations, to require immunity in approximately 70–80% of the population. However, this number will increase as newer variants arise with higher R 0 and increased transmissibility [64]. For many viruses, the more it circulates in a popula- tion, the more opportunities it has to replicate and/or mutate; SARS-CoV-2 has demonstrated this abil- ity [65]. These mutations have the potential to produce more transmissible and more virulent strains of SARS- CoV-2. For example, the 501Y mutation (present in the B.1.1.7 or alpha variant) and the L452R mutation (pre- sent in the B.1.617.2 or delta variant) are both associ- ated with higher levels of transmissibility [66].
eBook - PDFTruth, Lies, and Public Health
How We Are Affected When Science and Politics Collide
- Madelon L. Finkel(Author)
- 2007(Publication Date)
- Praeger(Publisher)
The eradication of smallpox worldwide is undoubtedly one of the most spectacular public health initiatives of all time. Vaccination not only protects an individual from disease, but it also has the dual role of protecting the community at large from disease outbreaks. For dis- ease to spread there must be a pool of susceptible people in whom the bacteria or virus can grow. Ironically, those who elect not to vaccinate themselves or their children are actually benefiting from those who are vaccinated. This con- cept is referred to as “Herd Immunity.” When a disease spreads from one human to another, it requires both an infected person to spread it and a suscep- tible person to catch it. Herd Immunity works by decreasing the number of sus- ceptible individuals, and when this number drops low enough, the disease will disappear from the community because there are not enough people to continue the catch-and-infect cycle. The greater the proportion of vaccinated individuals, the more rapidly the disease will disappear. Once-common diseases such as pertussis, polio, smallpox, and measles have all but disappeared thanks to the large numbers of individuals who are vaccinated against these diseases. Peri- odically, however, there have been mini-outbreaks of disease for which there are vaccinations. For example, there continue to be outbreaks of measles (a particularly contagious, potentially serious disease) in the United States as well as around the world, primarily as a result of a pool of unvaccinated children. Those who are not vaccinated are at high risk of contracting this disease. 3 Because microbes know no foreign boundary, diseases in one part of the world can quickly and easily spread to other parts of the globe. As such, a uni- fied global vaccination policy is needed; how to achieve such a noble and important goal, however, is often not easily accomplished. Economics, politics, and social constraints can and do play important roles in disease-eradication programs.
eBook - PDF- David C. Wiley, Amy C. Cory, David C. Wiley, Amy C. Cory(Authors)
- 2013(Publication Date)
- SAGE Publications, Inc(Publisher)
334 Infectious Diseases: Policies The development of comprehensive animal guidelines and policies is another key intervention with relevance to many settings, including the school environment. Contacts with pets are involved in both the zoonotic (from animals to humans) and the relatively less appreciated and poorly under-stood, but equally important, reverse zoonotic (from humans to animals) transmission of pathogens. The Importance of Vaccination One of the interventions that significantly decreased morbidity and mortality from infectious diseases is vaccination. Vaccination is not solely an individual prophylactic measure, but additionally, represents a public intervention, and maintaining high vaccina-tion rates is key for the development of herd immu-nity. This term refers to the concept that, if sufficient individuals in a population are vaccinated against a pathogen, too few susceptible individuals remain to maintain the pathogen in the population. This allows an infectious disease to be controlled even when not every individual in the population is vac-cinated. Herd Immunity is particularly important for people who cannot be vaccinated for medical rea-sons, and depend on surrounding vaccinated indi-viduals for their protection. Nonmedical exemptions from vaccination, such as the ones based on reli-gious or philosophical grounds, increase the risk of infectious diseases in both exempt and nonexempt individuals, and multiple studies found an overlap between clusters of preventable infectious diseases and groups of children whose families requested reli-gious exemption from vaccination. Learning about the benefits, limitations, and adverse effects of vaccines, and encouraging and enforcing vaccination, except when medically con-traindicated, are important initiatives that further the goals of public health interventions, especially in the school environment.
eBook - PDF- Hambidge, Gove(Authors)
- 2021(Publication Date)
- Biotech(Publisher)
Chapter 3 Protective Mechanisms Against Disease Adolph Eichhorn, Merritt P. Sarles & N.R. Ellis 1 1 Adolph Eichhorn is Director of the Animal Disease Station; Merritt P. Sarles is Assistant Parasitologist, Zoological Division; and N.R. Ellis is Senior Chemist, Animal Nutrition Division, Bureau of Animal Industry. Dr. Eichhorn prepared portions of the text relating to bacterial and virus diseases; Dr. Sarles contributed the section on parasitic diseases; and Mr. Ellis prepared the section on nutrition and disease resistance. Probably the most brilliant achievement of modern medical science has been the gradual disclosure of nature’s methods of producing immunity against disease, and the use of these methods to protect human beings and animals by artificial immunization. Not only livestock producers but everyone should understand the fundamentals of this process. Bacterial and Virus Diseases In the prevention and treatment of diseases of animals a knowledge of the principles of immunity is highly desirable, especially when biological products, such as vaccines, bacterins, toxoids, and immune serum, are to be used. In its true sense immunity denotes complete resistance to a disease, but since all individuals of a species can seldom be made resistant enough to withstand severe exposure, the term is now used chiefly in a relative sense; that is, it does not necessarily mean absolute resistance, but signifies that the natural resistance, if any, of an individual has been increased to a certain degree, which may be slight or marked, usually the latter. Susceptibility is the opposite of resistance, denoting that an animal of a certain species or the large majority of animals in a given species may contract a disease readily if This ebook is exclusively for this university only. Cannot be resold/distributed. exposed to it. Natural and Acquired Immunity Immunity may be natural or acquired.
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