Immunisation and herd immunity

Biology Department, Imperial College, London, UK.
The Lancet (Impact Factor: 45.22). 04/1990; 335(8690):641-5. DOI: 10.1016/0140-6736(90)90420-A
Source: PubMed
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    • "A number of epidemiological studies have reported associations between childhood leukaemia and population mixing [1–4], suggesting a role for infections in disease aetiology. This association is based upon the premise that areas with high levels of population mixing are likely to exhibit higher prevalence and a greater range of infections [5]. Increased levels of population mixing can be considered as a risk factor for cancer through exposure to some unknown infectious agent(s) as proposed by Kinlen [1]. "
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    ABSTRACT: Background Little aetiological epidemiological research has been undertaken for major cancers occurring in teenagers and young adults (TYA). Population mixing, as a possible proxy for infectious exposure, has been well researched for childhood malignancies. We aimed to investigate effects of population mixing in this older age group using an English national cancer dataset. Methods Cases of leukaemia, lymphoma and central nervous system (CNS) tumours amongst 15–24 year olds in England (diagnosed 1996–2005) were included in the study. Data were obtained by ward of diagnosis and linked to 1991 census variables including population mixing (Shannon index); data on person-weighted population density and deprivation (Townsend score) were also used and considered as explanatory variables. Associations between TYA cancer incidence and census variables were investigated using negative binomial regression, and results presented as incidence rate ratios (IRR) with 95% confidence intervals (CI). Results A total of 6251 cases of leukaemia (21%), lymphoma (49%) and CNS tumours (30%) were analysed. Higher levels of population mixing were associated with a significant decrease in the incidence of CNS tumours (IRR = 0.83, 95% CI = 0.75-0.91), accounted for by astrocytomas and ‘other CNS tumours’; however, there was no association with leukaemia or lymphoma. Incidence of CNS tumours and lymphoma was 3% lower in more deprived areas (IRR = 0.97, 95% CI = 0.96-0.99 and IRR = 0.97, 95% CI =0.96-0.98 respectively). Population density was not associated with the incidence of leukaemia, lymphoma or CNS tumours. Conclusions Our results suggest a possible role for environmental risk factors with population correlates in the aetiology of CNS tumours amongst TYAs. Unlike studies of childhood cancer, associations between population mixing and the incidence of leukaemia and lymphoma were not observed.
    Full-text · Article · Sep 2014 · BMC Cancer
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    • "This evidence suggests that deer mouse density is an important predictor of SNV prevalence in mice and human cases of hantavirus pulmonary syndrome (Yates et al. 2002). High variability of deer mouse populations on some of the Channel Islands (Drost and Fellers 1991) may also influence transmission dynamics by creating years during which host density is below the basic reproductive rate of the pathogen, R 0 (Anderson and May 1990). The importance of population variability is underscored by recent models that show how high stochastic variability in rodent abundance may cause SNV prevalence to decline to very low levels for extended periods of time (Allen et al. 2006). "
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    ABSTRACT: The relative roles of top-down and bottom-up forces in affecting disease prevalence in wild hosts is important for understanding disease dynamics and human disease risk. We found that the prevalence of Sin Nombre virus (SNV), the agent of a severe disease in humans (hantavirus pulmonary syndrome), in island deer mice from the eight California Channel Islands was greater with increased precipitation (a measure of productivity), greater island area, and fewer species of rodent predators. In finding a strong signal of the ecological forces affecting SNV prevalence, our work highlights the need for future work to understand the relative importance of average rodent density, population fluctuations, behavior, and specialist predators as they affect SNV prevalence. In addition to illustrating the importance of both bottom-up and top-down limitation of disease prevalence, our results suggest that predator richness may have important bearing on the risk of exposure to animal-borne diseases that affect humans.
    Full-text · Article · May 2011 · The American Naturalist
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    • "The estimated herd immunity threshold for mumps ranges from 88% to 92% [39] [40]. If the effectiveness of 2MMR is estimated at 88–95%, even a 95% coverage brings the population level of immunity below this threshold [36]. "
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    ABSTRACT: The aim of the study was to investigate effectiveness of mumps MMR component in communities with high MMR coverage. Outbreak-related cases of mumps born between 1995 and 2005 notified to Navarre and Catalonia public health services during the period 2005-2007 were studied. Vaccine effectiveness (VE) and their 95%CI were calculated using the screening method. Of 47 confirmed, 85.1% immunized with at least one dose (1MMR) and 44.9% with two (2MMR). Estimated VE was 85.4% (95%CI: 67.3-93.4) for 1MMR and 88.5% (95%CI: 78.1-93.9) for 2MMR. High 2MMR coverage, improved confirmation techniques and further VE studies with all confirmed cases are needed to prevent further outbreaks.
    Full-text · Article · Mar 2010 · Vaccine
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