Herd Immunity: A Realistic Target?
Journal Title: Biomedical Journal of Scientific & Technical Research (BJSTR) - Year 2018, Vol 9, Issue 2
Abstract
In this mini-review herd immunity is discussed by reviewing some recent vaccination campaigns for HPV, MEN-C, MEN-W and Ebola. It is concluded that vaccination coverage is rapidly declining due to societal factors, financial and logistical hurdles. Herd immunity depends now on unpredictable herd effects, Secondary declining transmission dynamics and carriage figures favour strong herd effects. Different target populations in the MEN-W vaccination programs of the UK and the Netherlands don't improve public confidence in an anti-vaxxers climate. Herd immunity is not a realistic target anymore and is dependent on herd effects varying with vaccination coverage percentages and this should be explained to the public in a clear way.The term "herd immunity" was introduced a century ago and used widely after increasing use of vaccines and vaccination protocols in the process of eradication of diseases [1]. The definition of herd immunity varies by several authors. Some use it to describe the proportion immune among individuals in a population, others use it with reference to a particular threshold proportion of immune individuals that should lead to a decline in incidence of infection and still others use it to refer to a pattern of immunity that should protect a population from an invasion of a new infection [2]. A common implication of the term is that the risk of infection among susceptible individuals in a population is reduced by the presence and proximity of immune individuals, this is called the "herd effect" or indirect proportion [2]. Individual immunity is a powerful force affecting host health and pathogen evaluation. The effects of individual immunity also scale up to affect pathogen transmission dynamics and the success of vaccination campaigns for entire host populations. Population-scale immunity is often termed "herd immunity" [3]. Herd immunity should be in more than 80% of the population [4]. Apart from innate immunity, it may be acquired either naturally or artificially. If herd immunity is dependent on natural infection, the large proportion of individuals in the population must have been exposed with sufficient frequency to an infectious agent to become immune [5]. It is important to realize that the herd immunity threshold is calculated by mathematical models that can differ for different infectious agents and geographical sites [2]. As vaccines must overcome the challenges of poor immune responses in hosts and antigenic diversity in pathogens, public policy plays a critical role in achieving the high population vaccination rate to achieve herd immunity and freedom of disease [6].
Authors and Affiliations
Michael AB Naafs
Keywords
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- EP ID EP591745
- DOI 10.26717/BJSTR.2018.09.001779
- Views 185
- Downloads 0
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