Process models offer opportunities to explore the effectiveness of different programme and policy alternatives by varying input behaviours and model parameters to reflect programmatic/policy effects. The Asian Epidemic Model (AEM) has been designed to reflect the primary groups and transmission modes driving HIV transmission in Asia. The user adjusts AEM fitting parameters until HIV prevalence outputs from the model agree with observed epidemiological trends. The AEM resultant projections are closely tied to the epidemiological and behavioural data in the country. In Thailand and Cambodia they have shown good agreement with observed epidemiological trends in surveillance populations and with changes in HIV transmission modes, AIDS cases, male:female ratios over time, and other external validation checks. By varying the input behaviours and STI trends, one can examine the impact of different prevention efforts on the future course of the epidemic. In conclusion, the AEM is a semi-empirical model, which has worked well in Asian settings. It provides a useful tool for policy and programme analysis in Asian countries.I n contrast to the curve fitting approaches used in the UNAIDS workbooks 1 and the Estimation and Projection Package (EPP), 2 the Asian Epidemic Model (AEM) is a full process model that mathematically replicates the key processes driving HIV transmission in Asia. As a result it has more extensive epidemiological and behavioural input requirements but offers the ability, which these other packages cannot, to examine future scenarios in which prevention and care efforts induce behaviour change. This paper will describe the AEM, explain its use, and discuss actual applications.In 1998, Chin et al proposed that three major factors determined the spread of HIV in Asia: the general pattern of heterosexual risk behaviours, the percentage of men visiting sex workers, and the partner exchange rates of female sex workers.3 With support from the United States Agency for International Development, the AEM was developed to test this hypothesis by implementing a process model focused primarily on the most important transmission routes for HIV in Asia-sex work, marital sex, and injecting drug use-and then testing it against actual epidemiological trends in Asian countries. 4 The goal was to develop a model of sufficient complexity to capture the essential dynamics of Asian epidemics, while keeping it simple enough that behavioural and epidemiological inputs could be obtained from existing data sources.Two key design decisions were made. Firstly, the model would be semi-empirical, not theoretical in nature. It would be patterned after the dominant transmission modes in Asia with appropriate behavioural inputs. However, values for parameters such as HIV transmission probabilities and cofactors would be set on a country specific basis by comparing HIV trends generated by the model directly against observed epidemiological trends, rather than by assuming the parameters to have specific values a priori. Furthermore, impor...
The new methods and data implemented in the 2016 version of Spectrum allow national programs more flexibility in describing their programs and improve the estimates of key indicators and their uncertainty.
The declining trend in HIV transmission rates despite ever-growing prevalence indicates prevention success correlated with the national HIV/AIDS program. Data from subgroup analyses provide stronger evidence of prevention success than incidence alone, as this measure demonstrates the effect of efforts and accounts for the burden of disease in the population.
The paper estimates that under 2005 prices NAPHA will save life-years at approximately US$736 per life-year saved with first-line drugs alone and for approximately US$2145 per life-year if second-line drugs are included. Enhancing NAPHA with policies to recruit patients soon after they are first eligible for ART or to enhance their adherence would raise the cost per life-year saved, but the cost would be small per additional life-year saved, and is therefore justifiable. The fiscal burden of a policy including second as well as first-line drugs would be substantial, rising to 23% of the total health budget by 2014, but the authors judge this cost to be affordable given Thailand's strong overall economic performance. The paper estimates that a 90% reduction in the future cost of second-line therapy by the exercise of Thailand's World Trade Organization authority to issue compulsory licences would save the government approximately US$3.2 billion to 2025 and reduce the cost of NAPHA per life-year saved from US$2145 to approximately US$940.
BackgroundThis study aims to determine the maximum price at which HIV vaccination is cost-effective in the Thai healthcare setting. It also aims to identify the relative importance of vaccine characteristics and risk behavior changes among vaccine recipients to determine how they affect this cost-effectiveness.MethodsA semi-Markov model was developed to estimate the costs and health outcomes of HIV prevention programs combined with HIV vaccination in comparison to the existing HIV prevention programs without vaccination. The estimation was based on a lifetime horizon period (99 years) and used the government perspective. The analysis focused on both the general population and specific high-risk population groups. The maximum price of cost-effective vaccination was defined by using threshold analysis; one-way and probabilistic sensitivity analyses were performed. The study employed an expected value of perfect information (EVPI) analysis to determine the relative importance of parameters and to prioritize future studies.ResultsThe most expensive HIV vaccination which is cost-effective when given to the general population was 12,000 Thai baht (US$1 = 34 Thai baht in 2009). This vaccination came with 70% vaccine efficacy and lifetime protection as long as risk behavior was unchanged post-vaccination. The vaccine would be considered cost-ineffective at any price if it demonstrated low efficacy (30%) and if post-vaccination risk behavior increased by 10% or more, especially among the high-risk population groups. The incremental cost-effectiveness ratios were the most sensitive to change in post-vaccination risk behavior, followed by vaccine efficacy and duration of protection. The EVPI indicated the need to quantify vaccine efficacy, changed post-vaccination risk behavior, and the costs of vaccination programs.ConclusionsThe approach used in this study differentiated it from other economic evaluations and can be applied for the economic evaluation of other health interventions not available in healthcare systems. This study is important not only for researchers conducting future HIV vaccine research but also for policy decision makers who, in the future, will consider vaccine adoption.
Purpose of review To explore the comparative importance of HIV infections among key populations and their intimate partners as HIV epidemics evolve, and to review implications for guiding responses. Recent findings Even as concentrated epidemics evolve, new infections among current and former key population members and their intimate partners dominate new infections. Prevalent infections in the general population grow primarily because of key population turnover and infections among their intimate partners. In generalized epidemic settings, data and analysis on key populations are often inadequate to assess the impact of key population-focused responses, so they remain limited in coverage and under resourced. Models must incorporate downstream infections in comparing impacts of alternative responses. Summary Recognize that every epidemic is unique, moving beyond the overly simplistic concentrated/generalized epidemic paradigm that can misdirect resources. Guide HIV responses by gathering and using locally relevant data, understanding risk heterogeneity, and applying modeling at both national and sub-national levels to optimize resource allocations among different populations for greatest impact. Translate this improved understanding into clear, unequivocal advice for policymakers on where to focus for impact, breaking them free of the generalized/concentrated paradigm limiting their thinking and affecting their decisions.
This volume is a product of the staff of the International Bank for Reconstruction and Development / The World Bank. The findings, interpretations, and conclusions expressed in this volume do not necessarily reflect the views of the Executive Directors of The World Bank or the governments they represent. The World Bank does not guarantee the accuracy of the data included in this work. The boundaries, colors, denominations, and other information shown on any map in this work do not imply any judgement on the part of The World Bank concerning the legal status of any territory or the endorsement or acceptance of such boundaries. Rights and Permissions The material in this publication is copyrighted. Copying and/or transmitting portions or all of this work without permission may be a violation of applicable law. The International Bank for Reconstruction and Development / The World Bank encourages dissemination of its work and will normally grant permission to reproduce portions of the work promptly.
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