The cost-effectiveness of HIV prevention targeting: how much more bang for the buck?

Investigation of Early Syphilis Trends Among Men Who Have Sex With Men to Identify Gaps in Screening and Case-Finding in Baltimore City, Maryland

BACKGROUND

Syphilis incidence is increasing across the United States among men who have sex with men (MSM). Early latent (EL) versus primary and secondary (P&S) syphilis may be an indicator of delayed diagnosis and increased opportunity for transmission. To inform syphilis control strategies and identify potential gaps in case finding, we described recent syphilis trends among MSM and compared characteristics of syphilis cases by diagnosis stage.

METHODS

We used public health surveillance data on P&S and EL syphilis diagnoses reported to the Baltimore City Health Department between 2009 and 2015. Differences across diagnosis stage were assessed using Cochran-Armitage and χ tests.

RESULTS

Between 2009 and 2015, Baltimore City Health Department received 2436 reports of P&S and EL diagnoses. The majority (61%) of reports were among MSM, among whom 86% were black and 67% were human immunodeficiency virus (HIV)-infected. During this period, P&S and EL syphilis increased by 85% and 245%, respectively (P < 0.0001). MSM with EL versus P&S syphilis were similarly likely to be Black, more likely to be older (P < 0.05), HIV coinfected (P < 0.001), and diagnosed in private health care settings (P < 0.0001), but less likely to report multiple (P < 0.001) and anonymous sex partners (P < 0.001).

CONCLUSIONS

In Baltimore City, syphilis diagnoses, particularly EL diagnoses, are increasing rapidly and are concentrated among Black HIV-infected MSM. Significant gaps in identifying MSM with P&S syphilis may exist, specifically among HIV-infected MSM, and those diagnosed in private health care settings. Strategies to address these gaps may include local guidelines and provider education to screen MSM more frequently than CDC currently recommends and regardless of HIV status or risk.

The Impact of Ignoring Population Heterogeneity when Markov Models are Used in Cost-Effectiveness Analysis

Many factors related to the spread and progression of diseases vary throughout a population. This heterogeneity is frequently ignored in cost-effectiveness analyses by using aver-age or representative values or by considering multiple risk groups. The author explores the impact that such simplifying assumptions may have on the results and interpretation of cost-effectiveness analyses when Markov models are used to calculate the costs and health impact of interventions. A discrete-time Markov model for a disease is defined, and 5 potential interventions are considered. Health benefits, costs, and incremental cost-effectiveness ratios are calculated for each intervention. It is assumed that the population is heterogeneous with respect to the probability of becoming sick. Ignoring this heterogeneity may lead to optimistic or pessimistic estimates of cost-effectiveness ratios, depending on the intervention and, in some cases, the parameter values. Implications are discussed of this finding on the use of league tables and on comparisons of cost-effectiveness ratios versus commonly accepted threshold values.

Financing prevention: opportunities for economic analysis across the translational research cycle

Prevention advocates often make the case that preventive intervention not only improves public health and welfare but also can save public resources. Increasingly, evidence-based policy efforts considering prevention are focusing on how programs can save taxpayer resources from reduced burden on health, criminal justice, and social service systems. Evidence of prevention's return has begun to draw substantial investments from the public and private sector. Yet, translating prevention effectiveness into economic impact requires specific economic analyses to be employed across the stages of translational research. This work discusses the role of economic analysis in prevention science and presents key translational research opportunities to meet growing demand for estimates of prevention's economic and fiscal impact.

A systematic review of the effectiveness and cost-effectiveness of peer-based interventions to maintain and improve offender health in prison settings

Background

Offender health is deemed a priority issue by the Department of Health. Peer support is an established feature of prison life in England and Wales; however, more needs to be known about the effectiveness of peer-based interventions to maintain and improve health in prison settings.

Objectives

The study aimed to synthesise the evidence on peer-based interventions in prison settings by carrying out a systematic review and holding an expert symposium. Review questions were (1) what are the effects of peer-based interventions on prisoner health and the determinants of prisoner health?, (2) what are the positive and negative impacts on health services within prison settings of delivering peer-based interventions?, (3) how do the effects of peer-based approaches compare with those of professionally led approaches? and (4) what are the costs and cost-effectiveness of peer-based interventions in prison settings?

Data sources

For the systematic review, 20 electronic databases including MEDLINE, PsycINFO, the Cumulative Index to Nursing and Allied Health Literature and EMBASE were searched from 1985. Grey literature and relevant websites were also searched. To supplement the review findings 58 delegates, representing a variety of organisations, attended an expert symposium, which provided contextual information.

Review methods

Two reviewers independently selected studies using the following inclusion criteria: population – prisoners resident in prisons and young offender institutions; intervention – peer-based interventions; comparators: review questions 3 and 4 compared peer-led and professionally led approaches; outcomes – prisoner health or determinants of health, organisational/process outcomes or views of prison populations; study design: quantitative, qualitative and mixed-methods evaluations. Two reviewers extracted data and assessed validity using piloted electronic forms and validity assessment criteria based on published checklists. Results from quantitative studies were combined using narrative summary and meta-analysis when appropriate; results from qualitative studies were combined using thematic synthesis.

Results

A total of 15,320 potentially relevant papers were identified of which 57 studies were included in the effectiveness review and one study was included in the cost-effectiveness review; most were of poor methodological quality. A typology of peer-based interventions was developed. Evidence suggested that peer education interventions are effective at reducing risky behaviours and that peer support services provide an acceptable source of help within the prison environment and have a positive effect on recipients; the strongest evidence came from the Listener scheme. Consistent evidence from many predominantly qualitative studies suggested that being a peer deliverer was associated with positive effects across all intervention types. There was limited evidence about recruitment of peer deliverers. Recurring themes were the importance of prison managerial and staff support for schemes to operate successfully, and risk management. There was little evidence on the cost-effectiveness of peer-based interventions. An economic model, developed from the results of the effectiveness review, although based on data of variable quality and a number of assumptions, showed the cost-effectiveness of peer-led over professionally led education in prison for the prevention of human immunodeficiency virus (HIV) infection.

Limitations

The 58 included studies were, on the whole, of poor methodological quality.

Conclusions

There is consistent evidence from a large number of studies that being a peer worker is associated with positive health. Peer support services can also provide an acceptable source of help within the prison environment and can have a positive effect on recipients. This was confirmed by expert evidence. Research into cost-effectiveness is sparse but a limited HIV-specific economic model, although based on a number of assumptions and evidence of variable quality, showed that peer interventions were cost-effective compared with professionally led interventions. Well-designed intervention studies are needed to provide robust evidence including assessing outcomes for the target population, economic analysis of cost-effectiveness and impacts on prison health services. More research is needed to examine issues of reach, utilisation and acceptability from the perspective of recipients and those who choose not to receive peer support.

Study registration

This study was registered as PROSPERO CRD42012002349.

Funding

The National Institute for Health Research Health Services and Delivery Research programme.

Identifying and characterizing places for the targeted control of heterosexual HIV transmission in urban areas

Places with active HIV transmission may serve as key locations for targeted control. In 2008-2009, heterosexual sex partner venues in Baltimore, MD were identified using a three-phase process and characterized by the presence or absence of HIV cases. 1,594 participants aged 18-35 years were enrolled at 87 venues. The study yielded an overall HIV prevalence of 3.7 %; 42 % of venues had ≥1 case of HIV (i.e., HIV positive venues). In final age-adjusted models, HIV positive venues had 10 % more high HIV-risk sexual partnering (95 % CI 1.01, 1.19) and more than twice as much drug market activity (95 % CI 1.04, 6.46) compared to HIV negative venues. Commercial sex work, parenteral risk behavior and venue-level sex market activity were not significantly associated with HIV status of the venues. This study highlights characteristics of venues, such as drug market activity, that may be important in identifying places with active HIV transmission.

The case for transmissible antivirals to control population-wide infectious disease

Infectious disease control faces significant challenges including: how to therapeutically target the highest-risk populations, circumvent behavioral barriers, and overcome pathogen persistence and resistance mechanisms. We review a recently proposed solution to overcome these challenges: antivirals that transmit by 'piggybacking' on viral replication. These proposed antivirals, termed 'therapeutic interfering particles' (TIPs), are engineered molecular parasites of viruses that are designed to steal replication resources from the wild type virus. Depriving viruses of crucial replication machinery, TIPs would reduce viral loads. As obligate parasites, TIPs would transmit via the same risk factors and transmission routes as wild type viruses, automatically reaching high-risk populations, and thereby substantially limiting viral transmission even in resource-poor settings. Design issues and ethical/safety considerations of this proposed intervention are discussed.

Indices to measure risk of HIV acquisition in Rakai, Uganda

Introduction

Targeting most-at-risk individuals with HIV preventive interventions is cost-effective. We developed gender-specific indices to measure risk of HIV among sexually active individuals in Rakai, Uganda.

Methods

We used multivariable Cox proportional hazards models to estimate time-to-HIV infection associated with candidate predictors. Reduced models were determined using backward selection procedures with Akaike's information criterion (AIC) as the stopping rule. Model discrimination was determined using Harrell's concordance index (c index). Model calibration was determined graphically. Nomograms were used to present the final prediction models.

Results

We used samples of 7,497 women and 5,783 men. 342 new infections occurred among females (incidence 1.11/100 person years,) and 225 among the males (incidence 1.00/100 person years). The final model for men included age, education, circumcision status, number of sexual partners, genital ulcer disease symptoms, alcohol use before sex, partner in high risk employment, community type, being unaware of a partner's HIV status and community HIV prevalence. The Model's optimism-corrected c index was 69.1 percent (95% CI = 0.66, 0.73). The final women's model included age, marital status, education, number of sex partners, new sex partner, alcohol consumption by self or partner before sex, concurrent sexual partners, being employed in a high-risk occupation, having genital ulcer disease symptoms, community HIV prevalence, and perceiving oneself or partner to be exposed to HIV. The models optimism-corrected c index was 0.67 (95% CI = 0.64, 0.70). Both models were well calibrated.

Conclusion

These indices were discriminative and well calibrated. This provides proof-of-concept that population-based HIV risk indices can be developed. Further research to validate these indices for other populations is needed.

Autonomous targeting of infectious superspreaders using engineered transmissible therapies

Infectious disease treatments, both pharmaceutical and vaccine, face three universal challenges: the difficulty of targeting treatments to high-risk ‘superspreader’ populations who drive the great majority of disease spread, behavioral barriers in the host population (such as poor compliance and risk disinhibition), and the evolution of pathogen resistance. Here, we describe a proposed intervention that would overcome these challenges by capitalizing upon Therapeutic Interfering Particles (TIPs) that are engineered to replicate conditionally in the presence of the pathogen and spread between individuals — analogous to ‘transmissible immunization’ that occurs with live-attenuated vaccines (but without the potential for reversion to virulence). Building on analyses of HIV field data from sub-Saharan Africa, we construct a multi-scale model, beginning at the single-cell level, to predict the effect of TIPs on individual patient viral loads and ultimately population-level disease prevalence. Our results show that a TIP, engineered with properties based on a recent HIV gene-therapy trial, could stably lower HIV/AIDS prevalence by ∼30-fold within 50 years and could complement current therapies. In contrast, optimistic antiretroviral therapy or vaccination campaigns alone could only lower HIV/AIDS prevalence by <2-fold over 50 years. The TIP's efficacy arises from its exploitation of the same risk factors as the pathogen, allowing it to autonomously penetrate superspreader populations, maintain efficacy despite behavioral disinhibition, and limit viral resistance. While demonstrated here for HIV, the TIP concept could apply broadly to many viral infectious diseases and would represent a new paradigm for disease control, away from pathogen eradication but toward robust disease suppression.

We introduce a proposed intervention against infectious diseases that extends and optimizes the recognized benefit of ‘transmissible immunization’ that occurs with live-attenuated vaccines such as Oral Polio Vaccine (OPV), the vaccine chosen for the worldwide polio eradication campaign. The intervention proposed here is based upon Therapeutic Interfering Particles (TIPs) that are engineered to replicate only in the presence of the wildtype pathogen and act to inhibit the growth of the pathogen. Therefore TIPs ‘piggyback’ on the pathogen, leading to two important differences from live-attenuated vaccines: TIPs can only transmit from individuals already infected with wildtype pathogen, and TIPs could only revert to virulence in individuals already carrying the wild-type pathogen. Intriguingly, because TIPs spread between individuals using the same transmission routes as the pathogen, they automatically find their way to the populations at greatest risk of infection, thus circumventing the unsolved problem of how to identify superspreaders and target them for preventive measures. Based on clinical-trial data, we analyze the impact that TIP intervention would have on HIV/AIDS in sub-Saharan Africa and show that TIPs could lower HIV/AIDS prevalence more effectively than vaccines or drugs alone and, in fact, would effectively complement these other interventions.

Decision making for HIV prevention and treatment scale up: bridging the gap between theory and practice

BACKGROUND

Effectively controlling the HIV epidemic will require efficient use of limited resources. Despite ambitious global goals for HIV prevention and treatment scale up, few comprehensive practical tools exist to inform such decisions.

METHODS

We briefly summarize modeling approaches for resource allocation for epidemic control, and discuss the practical limitations of these models. We describe typical challenges of HIV resource allocation in practice and some of the tools used by decision makers. We identify the characteristics needed in a model that can effectively support planners in decision making about HIV prevention and treatment scale up.

RESULTS

An effective model to support HIV scale-up decisions will be flexible, with capability for parameter customization and incorporation of uncertainty. Such a model needs certain key technical features: it must capture epidemic effects; account for how intervention effectiveness depends on the target population and the level of scale up; capture benefit and cost differentials for packages of interventions versus single interventions, including both treatment and prevention interventions; incorporate key constraints on potential funding allocations; identify optimal or near-optimal solutions; and estimate the impact of HIV interventions on the health care system and the resulting resource needs. Additionally, an effective model needs a user-friendly design and structure, ease of calibration and validation, and accessibility to decision makers in all settings.

CONCLUSIONS

Resource allocation theory can make a significant contribution to decision making about HIV prevention and treatment scale up. What remains now is to develop models that can bridge the gap between theory and practice.

Human rights and HIV prevention, treatment, and care for people who inject drugs: key principles and research needs

Efforts to provide HIV prevention, treatment, and care to injecting drug users (IDU) are shaped by tensions between approaches that regard IDU as criminals and those regarding drug-dependent individuals as patients deserving treatment and human rights. Advocates for IDU health and human rights find common cause in urging greater attention to legal frameworks, the effects of police abuses, and the need for protections for particularly vulnerable populations including women and those in state custody. Arbitrary detention of drug users, and conditions of pretrial detention, offer examples of how HIV prevention and treatment are adversely impacted by human rights abuse. National commitments to universal access to prevention and treatment for injecting drug users, and the recognition that users of illicit substances do not forfeit their entitlement to health services or human dignity, offer a clear point of convergence for advocates for health and rights, and suggest directions for reform to increase availability of sterile injection equipment, opiate substitution treatment, and antiretroviral therapy. For IDU, protection of rights has particular urgency if universal access to HIV prevention and treatment is to become an achievable reality.

Outpatient substance abuse treatment and HIV prevention: an update

Testing and counseling, along with community outreach, have been identified as valuable in the prevention of human immunodeficiency virus (HIV) and other blood-borne diseases. This article assesses the extent to which outpatient substance abuse treatment (OSAT) programs provide such services. Longitudinal data for 1988-2000 were analyzed from the National Drug Abuse Treatment System Survey (NDATSS). Random-effects regression was used to examine factors associated with the provision of prevention services. HIV testing, which had became more common between 1990 and 1995, continued to proliferate between 1995 and 2000. The proportion of units that provide HIV testing and counseling increased from 66% to 86%. The proportion of units that provide HIV community outreach increased significantly before 1995 but then slightly decreased from 77% to 73% between 1995 and 2000. In conclusion, HIV testing and counseling widely proliferated in OSAT care. However, OSAT units remain less likely to offer HIV community outreach services.

Efficient allocation of resources to prevent HIV infection among injection drug users: the Prevention Point Philadelphia (PPP) needle exchange program

The objective of this study is to determine the allocation of resources within a multi-site needle exchange program (NEP) that achieves the largest possible reduction in new HIV infections at minimum cost. We present a model that relates the number of injection drug user (IDU) clients and the number of syringes exchanged per client to both the costs of the NEP and the expected reduction in HIV infections per unit time. We show that cost-effective allocation within a multi-site NEP requires that sites be located where the density of IDUs is highest, and that the number of syringes exchanged per client be equal across sites. We apply these optimal allocation rules to a specific multi-site needle exchange program, Prevention Point Philadelphia (PPP). This NEP, we find, needs to add 2 or 3 new sites in neighborhoods with the highest density of IDU AIDS cases, and to increase its total IDU client base by about 28%, from approximately 6400 to 8200 IDU clients. The case-study NEP also needs to increase its hours of operation at two existing sites, where the number of needles distributed per client is currently sub-optimal, by 50%. At the optimal allocation, the estimated cost per case of HIV averted would be dollar 2800 (range dollar 2300-dollar 4200). Such a favorable cost-effectiveness ratio derives primarily from PPP's low marginal costs per distributed needle.

Improved allocation of HIV prevention resources: using information about prevention program production functions

To allocate HIV prevention resources effectively, it is important to have information about the effectiveness of alternative prevention programs as a function of expenditure. We refer to this relationship as the "production function" for a prevention program. Few studies of HIV prevention programs have reported this relationship. This paper demonstrates the value of such information. We present a simple model for allocating HIV prevention resources, and apply the model to an illustrative HIV prevention resource allocation problem. We show that, without sufficient information about prevention program production functions, suboptimal decisions may be made. We show that epidemiologic data, such as estimates of HIV prevalence or incidence, may not provide enough information to support optimal allocation of HIV prevention resources. Our results suggest that good allocations can be obtained based on fairly basic information about prevention program production functions: an estimate of fixed cost plus a single estimate of cost and resulting risk reduction. We find that knowledge of production functions is most important when fixed cost is high and/or when the budget is a significantly constraining factor. We suggest that, at the minimum, future data collection on prevention program effectiveness should include fixed and variable cost estimates for the intervention when implemented at a "typical" level, along with a detailed description of the intervention and detailed description of costs by category.

Screening for depression in primary care: what do we still need to know?

The United States Preventive Services Task Force (USPSTF) recently issued the recommendation that primary care physicians screen adult patients for depression. A policy to screen primary care patients for depression has appeal as a strategy to reduce the personal and societal costs of undiagnosed and untreated depression. Such appeal may be justified if the evidence supports the screening policy in three areas: effectiveness, cost-effectiveness, and feasibility. The USPSTF recommendation leaves many issues in each of these areas unresolved and physicians are left the choice of two important program characteristics: screening instrument and screening interval. We discuss how uncertainties in the screening protocol and treatment process affect whether screening is an effective and cost-effective use of resources with respect to other health interventions. We suggest that targeting screening to groups at a higher risk for depression may lead to a more effective use of health care resources. A screening program may not be feasible even if effectiveness and cost-effectiveness are optimized. We discuss uncertainties in the USPSTF recommendation that affect the feasibility of implementing such a program in physicians' practices.

Resource allocation for control of infectious diseases in multiple independent populations: beyond cost-effectiveness analysis

Traditional cost-effectiveness analysis (CEA) assumes that program costs and benefits scale linearly with investment-an unrealistic assumption for epidemic control programs. This paper combines epidemic modeling with optimization techniques to determine the optimal allocation of a limited resource for epidemic control among multiple noninteracting populations. We show that the optimal resource allocation depends on many factors including the size of each population, the state of the epidemic in each population before resources are allocated (e.g. infection prevalence and incidence), the length of the time horizon, and prevention program characteristics. We establish conditions that characterize the optimal solution in certain cases.

Country response to HIV/AIDS: national health accounts on HIV/AIDS in Brazil, Guatemala, Honduras, Mexico and Uruguay

National expenditures on HIV/AIDS were estimated as summary indicators to assess the country's response to HIV/AIDS. The methodology is based on a matrix system describing the level and flow of health expenditures on HIV/AIDS: an adaptation of the National Health Accounts methods. The expenditures were classified by source (public, private, international), by the use of funds (prevention, care), by object, and by type of provider institution. The results are reported in US dollars using the official exchange rate for the year of estimation. For international comparisons monetary units were adjusted by the purchasing power parity (US dollars PPP). National HIV/AIDS total expenditures were: Guatemala US dollars PPP29.5 million, Uruguay US dollars PPP 32.5 million, Mexico US dollars PPP 257 million, and Brazil US dollars PPP 587.4 million during 1998, and Honduras US dollars PPP 33.9 million for 1999. The total HIV/AIDS expenditures per capita for 1998 were: Brazil US dollars 2.69, Mexico US dollars 1.25, Guatemala US dollars 1.08, Uruguay US dollars 6.63, and Honduras US dollars 3.6 for 1999. The 1998 distribution of the total HIV/AIDS expenditures in prevention and care were, respectively, Brazil 10 and 80%, Guatemala 15 and 70%, Mexico 29 and 66%, Uruguay 36 and 51%, and Honduras 28 and 65% for 1999. The share of total expenditures on antiretroviral drugs ranged from 52% in Guatemala to 75% in Brazil, even when the estimated coverage of antiretroviral therapy was close to 10% in Guatemala and universal in Brazil. The estimated flow from international sources per capita in 1998 was Uruguay US dollars 0.03, Brazil US dollars 0.24, Guatemala US dollars 0.11, Mexico US dollars 0.01, and Honduras US dollars 1.04 in 1999. The data allow international comparisons and provide critical information to improve equity and efficiency in the allocation of scarce resources. The National HIV/AIDS Accounts also constitute a powerful tool to describe the country's response to HIV/AIDS.

Optimal allocation of resources across four interventions for type 2 diabetes

BACKGROUND

Several interventions can be applied to prevent complications of type 2 diabetes. This article examines the optimal allocation of resources across 4 interventions to treat patients newly diagnosed with type 2 diabetes. The interventions are intensive glycemic control, intensified hypertension control, cholesterol reduction, and smoking cessation.

METHODS

A linear programming model was designed to select sets of interventions to maximize quality-adjusted life years (QALYs), subject to varied budget and equity constraints.

RESULTS

For no additional cost, approximately 211,000 QALYs can be gained over the lifetimes of all persons newly diagnosed with diabetes by implementing interventions rather than standard care. With increased availability of funds, additional health benefits can be gained but with diminishing marginal returns. The impact of equity constraints is extensive compared to the solution with the same intervention costs and no equity constraint. Under the conditions modeled, intensified hypertension control and smoking cessation interventions were provided most often, and intensive glycemic control and cholesterol reduction interventions were provided less often.

CONCLUSIONS

A resource allocation model identifies trade-offs involved when imposing budget and equity constraints on care for individuals with newly diagnosed diabetes.

Modeling condom-use stage of change in low-income, single, urban women

This study was undertaken to identify and test a model of the cognitive antecedents to condom use stage of change in low-income, single, urban women. A convenience sample of 537 women (M=30 years old) attending two urban primary health care settings in western New York State anonymously completed questionnaires based primarily on two leading social-cognitive models, the transtheoretical model and the information-motivation-behavioral skills model. We used structural equation modeling to examine the direct and indirect effects of HIV-related knowledge, social norms of discussing HIV risk and prevention, familiarity with HIV-infected persons, general readiness to change sexual behaviors, perceived vulnerability to HIV, and pros and cons of condom use on condom-use stage of change. The results indicated two models that differ by partner type. Condom-use stage of change in women with steady main partners was influenced most by social norms and the pros of condom use. Condom-use stage of change in women with "other" types (multiple, casual, or new) of sexual partners was influenced by HIV-related knowledge, general readiness to change sexual behaviors, and the pros of condom use. These findings suggest implications for developing gender-relevant HIV-prevention interventions.

Optimal investment in a portfolio of HIV prevention programs

OBJECTIVES

In this article, the authors determine the optimal allocation of HIV prevention funds and investigate the impact of different allocation methods on health outcomes.

METHODS

The authors present a resource allocation model that can be used to determine the allocation of HIV prevention funds that maximizes quality-adjusted life years (or life years) gained or HIV infections averted in a population over a specified time horizon. They apply the model to determine the allocation of a limited budget among 3 types of HIV prevention programs in a population of injection drug users and nonusers: needle exchange programs, methadone maintenance treatment, and condom availability programs. For each prevention program, the authors estimate a production function that relates the amount invested to the associated change in risky behavior.

RESULTS

The authors determine the optimal allocation of funds for both objective functions for a high-prevalence population and a low-prevalence population. They also consider the allocation of funds under several common rules of thumb that are used to allocate HIV prevention resources. It is shown that simpler allocation methods (e.g., allocation based on HIV incidence or notions of equity among population groups) may lead to alloctions that do not yield the maximum health benefit.

CONCLUSIONS

The optimal allocation of HIV prevention funds in a population depends on HIV prevalence and incidence, the objective function, the production functions for the prevention programs, and other factors. Consideration of cost, equity, and social and political norms may be important when allocating HIV prevention funds. The model presented in this article can help decision makers determine the health consequences of different allocations of funds.

AIDS policy modeling for the 21st century: an overview of key issues

Decisions about HIV prevention and treatment programs are based on factors such as program costs and health benefits, social and ethical issues, and political considerations. AIDS policy models--that is, models that evaluate the monetary and non-monetary consequences of decisions about HIV/AIDS interventions--can play a role in helping policy makers make better decisions. This paper provides an overview of the key issues related to developing useful AIDS policy models. We highlight issues of importance for researchers in the field of AIDS policy modeling as well as for policy makers. These include geographic area, setting, target groups, interventions, affordability and effectiveness of interventions, type and time horizon of policy model, and type of economic analysis. This paper is not intended to be an exhaustive review of the AIDS policy modeling literature, although many papers from the literature are discussed as examples; rather, we aim to convey the composition, achievements, and challenges of AIDS policy modeling.

Cost-effectiveness of the Mpowerment Project, a community-level intervention for young gay men

OBJECTIVES

Previous evaluation demonstrated that the Mpowerment Project community-level intervention for young gay men reduces HIV risk behaviors. The current analysis was undertaken to estimate the intervention's health and economic outcomes.

DESIGN/METHODS

We conducted a retrospective cost-effectiveness analysis. We estimated HIV infections averted, the gain in quality-adjusted life years (QALYs), cost per infection averted, and net cost. Using a population-level model, we portrayed two epidemic scenarios: the first with stable HIV prevalence and the other with rising HIV prevalence. Inputs included behavior change resulting from the intervention and program cost data. Cost was calculated from three perspectives: societal; societal excluding volunteer time; and that of a community-based organization (CBO). Outcomes were calculated for 1, 5 (baseline), and 20 years.

RESULTS

The Mpowerment Project averted an estimated 2.0 to 2.3 HIV infections in the first year (according to the epidemic scenario), 5.0 to 6.2 over 5 years, and 9.2 to 13.1 over 20 years. The societal cost per HIV infection averted was estimated at between $14,600 and $18,300 over 5 years. Costs per infection averted were 28% lower when excluding volunteer time and 35% lower from the CBO perspective. Net savings were $700,000 to $900,000 over 5 years from the societal perspective.

CONCLUSIONS

The Mpowerment Project is cost-effective compared with many other HIV prevention strategies. The cost per HIV infection prevented is far less than the lifetime medical costs of HIV disease.

Resource allocation for epidemic control over short time horizons

We present a model for allocation of epidemic control resources among a set of interventions. We assume that the epidemic is modeled by a general compartmental epidemic model, and that interventions change one or more of the parameters that describe the epidemic. Associated with each intervention is a 'production function' that relates the amount invested in the intervention to values of parameters in the epidemic model. The goal is to maximize quality-adjusted life years gained or the number of new infections averted over a fixed time horizon, subject to a budget constraint. Unlike previous models, our model allows for interacting populations and non-linear interacting production functions and does not require a long time horizon. We show that an analytical solution to the model may be difficult or impossible to derive, even for simple cases. Therefore, we derive a method of approximating the objective functions. We use the approximations to gain insight into the optimal resource allocation for three problem instances. We also develop heuristics for solving the general resource allocation problem. We present results of numerical studies using our approximations and heuristics. Finally, we discuss implications and applications of this work.

A benefit-cost analysis of syringe exchange programs

To date, a paucity of systematic economic evaluations have been applied to syringe exchange programs. In today's cost-conscious environment, with public health officials contending with restricted HIV prevention budgets, what amount of scarce resources should be allocated toward the operation of SEPs? To address this question, benefit-cost analyses emerge as useful strategies to inform decision-makers about which programs hold the most promise for preventing HIV infection among intravenous drug users. This review article balances the benefits of HIV prevention via syringe exchange against the costs of operating such programs.

Prevention of HIV infection through changes in sexual behavior

Ample evidence exists that behavioral interventions reduce high risk sexual behaviors and promote safer practices. Downstream interventions in settings attracting high risk patients work well, especially with infected persons to avert new infections. Preparing health care workers for intensive, skills-based interventions grounded in behavioral science theory would enhance primary prevention. Midstream interventions have reliably reduced risk in primary care and community settings. Adoption of comprehensive skills-based programs in schools is controversial but likely to improve outcomes. Upstream community approaches have slowed human immunodeficiency virus (HIV) incidence among men having sex with men. Upstream policy interventions remain underutilized in the U.S. but have been successful internationally. Needed are a national HIV prevention strategy and research linking behavior change to reduced HIV seroprevalence.

Cost effectiveness of Streetworks' needle exchange program of Edmonton

OBJECTIVE

To conduct a cost-effectiveness analysis of the Edmonton Streetworks needle exchange program, in terms of the additional cost per HIV infection averted. The main outcome measures were needle use with and without Streetworks, HIV cases averted, and program costs.

METHODS

We conducted interviews and HIV saliva tests on a sample of street-involved intravenous drug users (IDU) who are regular Streetworks' clients. Outcomes were used in a cost-effectiveness model.

RESULTS

It is projected that the program has a cost-effectiveness of $9,500 (Canadian) per HIV infection delayed for one year.

CONCLUSIONS

The discounted cost per case averted is less than the cost of a case of AIDS. Continuing the program is a dominant strategy.

Cost effectiveness of Streetworks' needle exchange program of Edmonton

OBJECTIVE

To conduct a cost-effectiveness analysis of the Edmonton Streetworks needle exchange program, in terms of the additional cost per HIV infection averted. The main outcome measures were needle use with and without Streetworks, HIV cases averted, and program costs.

METHODS

We conducted interviews and HIV saliva tests on a sample of street-involved intravenous drug users (IDU) who are regular Streetworks' clients. Outcomes were used in a cost-effectiveness model.

RESULTS

It is projected that the program has a cost-effectiveness of $9,500 (Canadian) per HIV infection delayed for one year.

CONCLUSIONS

The discounted cost per case averted is less than the cost of a case of AIDS. Continuing the program is a dominant strategy.

Implicit valuation of a blood-exclusion decision

This paper presents an implicit valuation of Israel's decision to exclude blood donations from Ethiopian immigrants. The approach adopts assumptions that deliberately overstate the public health effectiveness of this policy, for if such an analysis fails to justify exclusion on public health grounds, nothing will. Building on a recent (over)estimate of the number of infectious donations prevented by the ban, the analysis considers the cost of HIV-infectious donations entering the blood supply, the benefits of healthy donations, and the cost of needlessly screening blood that will be discarded without regard to the test result. The analysis also highlights the social costs of excluding donors on the basis of ethnicity. The possibility of downstream HIV transmission from transfusion recipients infected from contaminated blood is also considered. All such calculations are made in a manner that deliberately favors the exclusion decision. In spite of such a one-sided analysis, the author concludes that the exclusion policy is not justifiable on cost-benefit grounds if the social costs of exclusion exceed $218,000 per year, or $3.63 per Ethiopian immigrant annually.

HIV/AIDS in Pakistan: the context and magnitude of an emerging threat

STUDY OBJECTIVE

The objectives of this review were to: (1) assess the nature and comprehensiveness of information regarding HIV/AIDS in Pakistan; (2) to evaluate the extent of HIV/AIDS in Pakistan by epidemiological estimates; (3) to indicate the implications of the results for health policy in Pakistan and other regions at a similar stage in the epidemic.

DESIGN

A structured review of published, unpublished, and government literature was undertaken to collate all available information and present a descriptive epidemiological profile of HIV/AIDS in the country.

SETTING

Pakistan, a developing country in the South Asian region. National and regional information and analysis are presented in so far as the data allowed. Sample sizes varied from 1.35 million people screened at the national level to smaller studies of fewer than 100 screened.

RESULTS

Data pertaining to HIV/AIDS in Pakistan showed the best national estimates of HIV prevalence as 64 per 100,000 (0.064%). Within patients with sexually transmitted diseases the seroprevalence was as high as 6100 per 100,000 (6.1%); in men with extramarital contacts, 5400 per 100,000 (5.4%) and was as low as zero in some studied populations as well. The average age of onset was reported as 30 years. It is estimated that if all incident cases of AIDS were to die, there would be at least 5000 deaths annually attributable to HIV/AIDS.

CONCLUSION

Coupled with the extremely low awareness of HIV/AIDS in Pakistan, as well as growing number of cases, the AIDS epidemic is poised to take a hold in Pakistan. The presence of additional risk factors such as unscreened blood, and low condom use rates make the situation fertile for AIDS to become a major public health issue. Pakistan's health policy must be proactive in tackling this emerging health threat.