Portfolios of biomedical HIV interventions in South Africa: a cost-effectiveness analysis

Health Economics Research on Non-surgical Biomedical HIV Prevention: Identifying Gaps and Proposing a Way Forward

BACKGROUND AND OBJECTIVE

Although HIV prevention science has advanced over the last four decades, evidence suggests that prevention technologies do not always reach their full potential. Critical health economics evidence at appropriate decision-making junctures, particularly early in the development process, could help identify and address potential barriers to the eventual uptake of future HIV prevention products. This paper aims to identify key evidence gaps and propose health economics research priorities for the field of HIV non-surgical biomedical prevention.

METHODS

We used a mixed-methods approach with three distinct components: (i) three systematic literature reviews (costs and cost effectiveness, HIV transmission modelling and quantitative preference elicitation) to understand health economics evidence and gaps in the peer-reviewed literature; (ii) an online survey with researchers working in this field to capture gaps in yet-to-be published research (recently completed, ongoing and future); and (iii) a stakeholder meeting with key global and national players in HIV prevention, including experts in product development, health economics research and policy uptake, to uncover further gaps, as well as to elicit views on priorities and recommendations based on (i) and (ii).

RESULTS

Gaps in the scope of available health economics evidence were identified. Little research has been carried out on certain key populations (e.g. transgender people and people who inject drugs) and other vulnerable groups (e.g. pregnant people and people who breastfeed). Research is also lacking on preferences of community actors who often influence or enable access to health services among priority populations. Oral pre-exposure prophylaxis, which has been rolled out in many settings, has been studied in depth. However, research on newer promising technologies, such as long-acting pre-exposure prophylaxis formulations, broadly neutralising antibodies and multipurpose prevention technologies, is lacking. Interventions focussing on reducing intravenous and vertical transmission are also understudied. A disproportionate amount of evidence on low- and middle-income countries comes from two countries (South Africa and Kenya); evidence from other countries in sub-Saharan Africa as well as other low- and middle-income countries is needed. Further, data are needed on non-facility-based service delivery modalities, integrated service delivery and ancillary services. Key methodological gaps were also identified. An emphasis on equity and representation of heterogeneous populations was lacking. Research rarely acknowledged the complex and dynamic use of prevention technologies over time. Greater efforts are needed to collect primary data, quantify uncertainty, systematically compare the full range of prevention options available, and validate pilot and modelling data once interventions are scaled up. Clarity on appropriate cost-effectiveness outcome measures and thresholds is also lacking. Lastly, research often fails to reflect policy-relevant questions and approaches.

CONCLUSIONS

Despite a large body of health economics evidence on non-surgical biomedical HIV prevention technologies, important gaps in the scope of evidence and methodology remain. To ensure that high-quality research influences key decision-making junctures and facilitates the delivery of prevention products in a way that maximises impact, we make five broad recommendations related to: improved study design, an increased focus on service delivery, greater community and stakeholder engagement, the fostering of an active network of partners across sectors and an enhanced application of research.

Implementation and resource needs for long-acting PrEP in low- and middle-income countries: a scoping review

INTRODUCTION

Several low- and middle-income countries (LMICs) are preparing to introduce long-acting pre-exposure prophylaxis (LAP). Amid multiple pre-exposure prophylaxis (PrEP) options and constrained funding, decision-makers could benefit from systematic implementation planning and aligned costs. We reviewed national costed implementation plans (CIPs) to describe relevant implementation inputs and activities (domains) for informing the costed rollout of LAP. We assessed how primary costing evidence aligned with those domains.

METHODS

We conducted a rapid review of CIPs for oral PrEP and family planning (FP) to develop a consensus of implementation domains, and a scoping review across nine electronic databases for publications on PrEP costing in LMICs between January 2010 and June 2022. We extracted cost data and assessed alignment with the implementation domains and the Global Health Costing Consortium principles.

RESULTS

We identified 15 implementation domains from four national PrEP plans and FP-CIP template; only six were in all sources. We included 66 full-text manuscripts, 10 reported LAP, 13 (20%) were primary cost studies-representing seven countries, and none of the 13 included LAP. The 13 primary cost studies included PrEP commodities (n = 12), human resources (n = 11), indirect costs (n = 11), other commodities (n = 10), demand creation (n = 9) and counselling (n = 9). Few studies costed integration into non-HIV services (n = 5), above site costs (n = 3), supply chains and logistics (n = 3) or policy and planning (n = 2), and none included the costs of target setting, health information system adaptations or implementation research. Cost units and outcomes were variable (e.g. average per person-year).

DISCUSSION

LAP planning will require updating HIV prevention policies, technical assistance for logistical and clinical support, expanding beyond HIV platforms, setting PrEP achievement targets overall and disaggregated by method, extensive supply chain and logistics planning and support, as well as updating health information systems to monitor multiple PrEP methods with different visit schedules. The 15 implementation domains were variable in reviewed studies. PrEP primary cost and budget data are necessary for new product introduction and should match implementation plans with financing.

CONCLUSIONS

As PrEP services expand to include LAP, decision-makers need a framework, tools and a process to support countries in planning the systematic rollout and costing for LAP.

Infectious Disease Modelling of HIV Prevention Interventions: A Systematic Review and Narrative Synthesis of Compartmental Models

BACKGROUND

The HIV epidemic remains a major public health problem. Critical to transmission control are HIV prevention strategies with new interventions continuing to be developed. Mathematical models are important for understanding the potential impact of these interventions and supporting policy decisions. This systematic review aims to answer the following question: when a new HIV prevention intervention is being considered or designed, what information regarding it is necessary to include in a compartmental model to provide useful insights to policy makers? The primary objective of this review is therefore to assess suitability of current compartmental HIV prevention models for informing policy development.

METHODS

Articles published in EMBASE, Medline, Econlit, and Global Health were screened. Included studies were identified using permutations of (i) HIV, (ii) pre-exposure prophylaxis (PrEP), circumcision (both voluntary male circumcision [VMMC] and early-infant male circumcision [EIMC]), and vaccination, and (iii) modelling. Data extraction focused on study design, model structure, and intervention incorporation into models. Article quality was assessed using the TRACE (TRAnsparent and Comprehensive Ecological modelling documentation) criteria for mathematical models.

RESULTS

Of 837 articles screened, 48 articles were included in the review, with 32 unique mathematical models identified. The substantial majority of studies included PrEP (83%), whilst fewer modelled circumcision (54%), and only a few focussed on vaccination (10%). Data evaluation, implementation verification, and model output corroboration were identified as areas of poorer model quality. Parameters commonly included in the mathematical models were intervention uptake and effectiveness, with additional intervention-specific common parameters identified. We identified key modelling gaps; critically, models insufficiently incorporate multiple interventions acting simultaneously. Additionally, population subgroups were generally poorly represented-with future models requiring improved incorporation of ethnicity and sexual risk group stratification-and many models contained inappropriate data in parameterisation which will affect output accuracy.

CONCLUSIONS

This review identified gaps in compartmental models to date and suggests areas of improvement for models focusing on new prevention interventions. Resolution of such gaps within future models will ensure greater robustness and transparency, and enable more accurate assessment of the impact that new interventions may have, thereby providing more meaningful guidance to policy makers.

Costs and Cost-Effectiveness of Biomedical, Non-Surgical HIV Prevention Interventions: A Systematic Literature Review

BACKGROUND

Considerable evidence on the costs and cost-effectiveness of biomedical, non-surgical interventions to prevent human immunodeficiency virus (HIV) transmission has been generated over the last decade. This study aims to synthesize findings and identify remaining knowledge gaps to suggest future research priorities.

METHODS

A systematic literature review was carried out in August 2020 using the MEDLINE, Embase, Global Health and EconLit databases to retrieve economic evaluations and costing studies of oral pre-exposure prophylaxis (PrEP), injectable long-acting PrEP, vaginal microbicide rings and gels, HIV vaccines and broadly neutralizing antibodies. Studies reporting costs from the provider or societal perspective were included in the analysis. Those reporting on behavioural methods of prevention, condoms and surgical approaches (voluntary medical male circumcision) were excluded. The quality of reporting of the included studies was assessed using published checklists.

RESULTS

We identified 3007 citations, of which 87 studies were retained. Most were set in low- and middle-income countries (LMICs; n = 53) and focused on the costs and/or cost-effectiveness of oral PrEP regimens (n = 70). Model-based economic evaluations were the most frequent study design; only two trial-based cost-effectiveness analyses and nine costing studies were found. Less than half of the studies provided practical details on how the intervention would be delivered by the health system, and only three of these, all in LMICs, explicitly focused on service integration and its implication for delivery costs. 'Real-world' programme delivery mechanisms and costs of intervention delivery were rarely considered. PrEP technologies were generally found to be cost-effective only when targeting high-risk subpopulations. Single-dose HIV vaccines are expected to be cost-effective for all groups despite substantial uncertainty around pricing.

CONCLUSIONS

A lack of primary, detailed and updated cost data, including above-service level costs, from a variety of settings makes it difficult to evaluate the cost-effectiveness of specific delivery modes at scale, or to evaluate strategies for services integration. Closing this evidence gap around real-world implementation is vital, not least because the strategies targeting high-risk groups that are recommended by PrEP models may incur substantially higher costs and be of limited practical feasibility in some settings.

Mapping age- and sex-specific HIV prevalence in adults in sub-Saharan Africa, 2000-2018

BACKGROUND

Human immunodeficiency virus and acquired immune deficiency syndrome (HIV/AIDS) is still among the leading causes of disease burden and mortality in sub-Saharan Africa (SSA), and the world is not on track to meet targets set for ending the epidemic by the Joint United Nations Programme on HIV/AIDS (UNAIDS) and the United Nations Sustainable Development Goals (SDGs). Precise HIV burden information is critical for effective geographic and epidemiological targeting of prevention and treatment interventions. Age- and sex-specific HIV prevalence estimates are widely available at the national level, and region-wide local estimates were recently published for adults overall. We add further dimensionality to previous analyses by estimating HIV prevalence at local scales, stratified into sex-specific 5-year age groups for adults ages 15-59 years across SSA.

METHODS

We analyzed data from 91 seroprevalence surveys and sentinel surveillance among antenatal care clinic (ANC) attendees using model-based geostatistical methods to produce estimates of HIV prevalence across 43 countries in SSA, from years 2000 to 2018, at a 5 × 5-km resolution and presented among second administrative level (typically districts or counties) units.

RESULTS

We found substantial variation in HIV prevalence across localities, ages, and sexes that have been masked in earlier analyses. Within-country variation in prevalence in 2018 was a median 3.5 times greater across ages and sexes, compared to for all adults combined. We note large within-district prevalence differences between age groups: for men, 50% of districts displayed at least a 14-fold difference between age groups with the highest and lowest prevalence, and at least a 9-fold difference for women. Prevalence trends also varied over time; between 2000 and 2018, 70% of all districts saw a reduction in prevalence greater than five percentage points in at least one sex and age group. Meanwhile, over 30% of all districts saw at least a five percentage point prevalence increase in one or more sex and age group.

CONCLUSIONS

As the HIV epidemic persists and evolves in SSA, geographic and demographic shifts in prevention and treatment efforts are necessary. These estimates offer epidemiologically informative detail to better guide more targeted interventions, vital for combating HIV in SSA.

Potential Impact and Cost-Effectiveness of Condomless-Sex-Concentrated PrEP in KwaZulu-Natal Accounting for Drug Resistance

INTRODUCTION

Oral preexposure prophylaxis (PrEP) in the form of tenofovir-disoproxil-fumarate/emtricitabine is being implemented in selected sites in South Africa. Addressing outstanding questions on PrEP cost-effectiveness can inform further implementation.

METHODS

We calibrated an individual-based model to KwaZulu-Natal to predict the impact and cost-effectiveness of PrEP, with use concentrated in periods of condomless sex, accounting for effects on drug resistance. We consider (1) PrEP availability for adolescent girls and young women aged 15-24 years and female sex workers, and (2) availability for everyone aged 15-64 years. Our primary analysis represents a level of PrEP use hypothesized to be attainable by future PrEP programs.

RESULTS

In the context of PrEP use in adults aged 15-64 years, there was a predicted 33% reduction in incidence and 36% reduction in women aged 15-24 years. PrEP was cost-effective, including in a range of sensitivity analyses, although with substantially reduced (cost) effectiveness under a policy of ART initiation with efavirenz- rather than dolutegravir-based regimens due to PrEP undermining ART effectiveness by increasing HIV drug resistance.

CONCLUSIONS

PrEP use concentrated during time periods of condomless sex has the potential to substantively impact HIV incidence and be cost-effective.

The impact, cost and cost-effectiveness of oral pre-exposure prophylaxis in sub-Saharan Africa: a scoping review of modelling contributions and way forward

INTRODUCTION

Oral pre-exposure prophylaxis (PrEP) is a new form of HIV prevention being considered for inclusion in national prevention portfolios. Many mathematical modelling studies have been undertaken that speak to the impact, cost and cost-effectiveness of PrEP programmes. We assess the available evidence from mathematical modelling studies to inform programme planning and policy decision making for PrEP and further research directions.

METHODS

We conducted a scoping review of the published modelling literature. Articles published in English which modelled oral PrEP in sub-Saharan Africa, or non-specific settings with relevance to generalized HIV epidemic settings, were included. Data were extracted for the strategies of PrEP use modelled, and the impact, cost and cost-effectiveness of PrEP for each strategy. We define an algorithm to assess the quality and relevance of studies included, summarize the available evidence and identify the current gaps in modelling. Recommendations are generated for future modelling applications and data collection.

RESULTS AND DISCUSSION

We reviewed 1924 abstracts and included 44 studies spanning 2007 to 2017. Modelling has reported that PrEP can be a cost-effective addition to HIV prevention portfolios for some use cases, but also that it would not be cost-effective to fund PrEP before other prevention interventions are expanded. However, our assessment of the quality of the modelling indicates cost-effectiveness analyses failed to comply with standards of reporting for economic evaluations and the assessment of relevance highlighted that both key parameters and scenarios are now outdated. Current evidence gaps include modelling to inform service development using updated programmatic information and ex post modelling to evaluate and inform efficient deployment of resources in support of PrEP, especially among key populations, using direct evidence of cost, adherence and uptake patterns.

CONCLUSIONS

Updated modelling which more appropriately captures PrEP programme delivery, uses current intervention scenarios, and is parameterized with data from demonstration and implementation projects is needed in support of more conclusive findings and actionable recommendations for programmes and policy. Future analyses should address these issues, aligning with countries to support the needs of programme planners and decision makers for models to more directly inform programme planning and policy.

Cost-effectiveness of HIV Prevention Interventions in Sub-Saharan Africa: A Systematic Review

BACKGROUND

Sub-Saharan Africa carries the highest HIV burden globally. It is important to understand how interventions cost-effectively fit within guidelines and implementation plans, especially in low- and middle-income settings. We reviewed the evidence from economic evaluations of HIV prevention interventions in sub-Saharan Africa to help inform the allocation of limited resources.

METHODS

We searched PubMed, Web of Science, Econ-Lit, Embase, and African Index Medicus. We included studies published between January 2009 and December 2018 reporting cost-effectiveness estimates of HIV prevention interventions. We extracted health outcomes and cost-effectiveness ratios (CERs) and evaluated study quality using the CHEERS checklist.

FINDINGS

60 studies met the full inclusion criteria. Prevention of mother-to-child transmission interventions had the lowest median CERs ($1144/HIV infection averted and $191/DALY averted), while pre-exposure prophylaxis interventions had the highest ($13,267/HIA and $799/DALY averted). Structural interventions (partner notification, cash transfer programs) have similar CERs ($3576/HIA and $392/DALY averted) to male circumcision ($2965/HIA) and were more favourable to treatment-as-prevention interventions ($7903/HIA and $890/DALY averted). Most interventions showed increased cost-effectiveness when prioritizing specific target groups based on age and risk.

INTERPRETATION

The presented cost-effectiveness information can aid policy makers and other stakeholders as they develop guidelines and programming for HIV prevention plans in resource-constrained settings.

A dynamic Bayesian Markov model for health economic evaluations of interventions in infectious disease

BACKGROUND

Health economic evaluations of interventions in infectious disease are commonly based on the predictions of ordinary differential equation (ODE) systems or Markov models (MMs). Standard MMs are static, whereas ODE systems are usually dynamic and account for herd immunity which is crucial to prevent overestimation of infection prevalence. Complex ODE systems including distributions on model parameters are computationally intensive. Thus, mainly ODE-based models including fixed parameter values are presented in the literature. These do not account for parameter uncertainty. As a consequence, probabilistic sensitivity analysis (PSA), a crucial component of health economic evaluations, cannot be conducted straightforwardly.

METHODS

We present a dynamic MM under a Bayesian framework. We extend a static MM by incorporating the force of infection into the state allocation algorithm. The corresponding output is based on dynamic changes in prevalence and thus accounts for herd immunity. In contrast to deterministic ODE-based models, PSA can be conducted straightforwardly. We introduce a case study of a fictional sexually transmitted infection and compare our dynamic Bayesian MM to a deterministic and a Bayesian ODE system. The models are calibrated to simulated time series data.

RESULTS

By means of the case study, we show that our methodology produces outcome which is comparable to the "gold standard" of the Bayesian ODE system.

CONCLUSIONS

In contrast to ODE systems in the literature, the dynamic MM includes distributions on all model parameters at manageable computational effort (including calibration). The run time of the Bayesian ODE system is 15 times longer.

Cost and cost-effectiveness analysis of pre-exposure prophylaxis among men who have sex with men in two hospitals in Thailand

INTRODUCTION

In 2014, the Government of Thailand recommended pre-exposure prophylaxis (PrEP) as an additional HIV prevention programme within Thailand's National Guidelines on HIV/AIDS Treatment Prevention. However, to date implementation and uptake of PrEP programmes have been limited, and evidence on the costs and the epidemiological and economic impact is not available.

METHODS

We estimated the costs associated with PrEP provision among men having sex with men (MSM) participating in a facility-based, prospective observational cohort study: the Test, Treat and Prevent HIV Programme in Thailand. We created a suite of scenarios to estimate the cost-effectiveness of PrEP and sensitivity of the results to the model input parameters, including PrEP programme effectiveness, PrEP uptake among high-risk and low-risk MSM, baseline and future antiretroviral therapy (ART) coverage, condom use, unit cost of delivering PrEP, and the discount rate.

RESULTS

Drug costs accounted for 82.5% of the total cost of providing PrEP, followed by lab testing (8.2%) and personnel costs (7.8%). The estimated costs of providing the PrEP package in accordance with the national recommendation ranges from US$223 to US$311 per person per year. Based on our modelling results, we estimate that PrEP would be cost-effective when provided to either high-risk or all MSM. However, we found that the programme would be approximately 32% more cost-effective if offered to high-risk MSM than it would be if offered to all MSM, with an incremental cost-effectiveness ratio of US$4,836 per disability-adjusted life years (DALY) averted and US$7,089 per DALY averted respectively. Cost-effectiveness acceptability curves demonstrate that 80% of scenarios would be cost-effective when PrEP is provided solely to higher-risk MSM.

CONCLUSION

We provide the first estimates on cost and cost-effectiveness of PrEP in the Asia-Pacific region, and offer insights on how to deliver PrEP in combination with ART. While the high drug cost poses a budgeting challenge, incorporating PrEP delivery into an existing ART programme could be a cost-effective strategy to prevent HIV infections among MSM in Thailand.

Combined interventions to reduce HIV incidence in KwaZulu-Natal: a modelling study

BACKGROUND

Combined prevention interventions, including early antiretroviral therapy initiation, may substantially reduce HIV incidence in hyperendemic settings. Our aim was to assess the potential short-term impact of combined interventions on HIV spreading in the adult population of Mbongolwane and Eshowe (KwaZulu-Natal, South Africa) using sex- and age-specific scenarios, and age-targeted interventions.

METHODS

A mathematical model was used with data on adults (15-59 years) from the Mbongolwane and Eshowe HIV Impact in Population Survey to compare the effects of various interventions on the HIV incidence rate. These interventions included increase in antiretroviral therapy (ART) coverage with extended eligibility criteria, increase in voluntary medical male circumcision (VMMC), and implementation of pre-exposure prophylaxis (PrEP) among women.

RESULTS

With no additional interventions to the ones in place at the time of the survey (ART at CD4 < 350 and VMMC), incidence will decrease by 24% compared to the baseline rate. The implementation of "ART at CD4<500" or "ART for all" would reduce further the incidence rate by additional 8% and 15% respectively by 4 years and 20% and 34% by 10 years. Impacts would be higher with age-targeted scenarios than without.

CONCLUSIONS

In Mbongolwane and Eshowe, implementation of the new South African guidelines, recommending ART initiation regardless of CD4 count, would accelerate incidence reduction. In this setting, combining these guidelines, VMMC, and PrEP among young women could be an effective strategy in reducing the incidence to low levels.

Universal test, treat, and keep: improving ART retention is key in cost-effective HIV control in Uganda

Background

With ambitious new UNAIDS targets to end AIDS by 2030, and new WHO treatment guidelines, there is increased interest in the best way to scale-up ART coverage. We investigate the cost-effectiveness of various ART scale-up options in Uganda.

Methods

Individual-based HIV/ART model of Uganda, calibrated using history matching. 22 ART scale-up strategies were simulated from 2016 to 2030, comprising different combinations of six single interventions (1. increased HIV testing rates, 2. no CD4 threshold for ART initiation, 3. improved ART retention, 4. increased ART restart rates, 5. improved linkage to care, 6. improved pre-ART care). The incremental net monetary benefit (NMB) of each intervention was calculated, for a wide range of different willingness/ability to pay (WTP) per DALY averted (health-service perspective, 3% discount rate).

Results

For all WTP thresholds above $210, interventions including removing the CD4 threshold were likely to be most cost-effective. At a WTP of $715 (1 × per-capita-GDP) interventions to improve linkage to and retention/re-enrolment in HIV care were highly likely to be more cost-effective than interventions to increase rates of HIV testing. At higher WTP (> ~ $1690), the most cost-effective option was ‘Universal Test, Treat, and Keep’ (UTTK), which combines interventions 1–5 detailed above.

Conclusions

Our results support new WHO guidelines to remove the CD4 threshold for ART initiation in Uganda. With additional resources, this could be supplemented with interventions aimed at improving linkage to and/or retention in HIV care. To achieve the greatest reductions in HIV incidence, a UTTK policy should be implemented.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2420-y) contains supplementary material, which is available to authorized users.

Designing an optimal HIV programme for South Africa: Does the optimal package change when diminishing returns are considered?

Background

South Africa has a large domestically funded HIV programme with highly saturated coverage levels for most prevention and treatment interventions. To further optimise its allocative efficiency, we designed a novel optimisation method and examined whether the optimal package of interventions changes when interaction and non-linear scale-up effects are incorporated into cost-effectiveness analysis.

Methods

The conventional league table method in cost-effectiveness analysis relies on the assumption of independence between interventions. We added methodology that allowed the simultaneous consideration of a large number of HIV interventions and their potentially diminishing marginal returns to scale. We analysed the incremental cost effectiveness ratio (ICER) of 16 HIV interventions based on a well-calibrated epidemiological model that accounted for interaction and non-linear scale-up effects, a custom cost model, and an optimisation routine that iteratively added the most cost-effective intervention onto a rolling baseline before evaluating all remaining options. We compared our results with those based on a league table.

Results

The rank order of interventions did not differ substantially between the two methods- in each, increasing condom availability and male medical circumcision were found to be most cost-effective, followed by anti-retroviral therapy at current guidelines. However, interventions were less cost-effective throughout when evaluated under the optimisation method, indicating substantial diminishing marginal returns, with ICERs being on average 437% higher under our optimisation routine.

Conclusions

Conventional league tables may exaggerate the cost-effectiveness of interventions when programmes are implemented at scale. Accounting for interaction and non-linear scale-up effects provides more realistic estimates in highly saturated real-world settings.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-017-4023-3) contains supplementary material, which is available to authorized users.

The Price of Prevention: Cost Effectiveness of Biomedical HIV Prevention Strategies in South Africa

BACKGROUND

South Africa has the highest global burden of human immunodefciency virus [HIV]. The study compared the cost-effectiveness of individual and combination HIV preventive strategies against the current rollout of ART and possible ART scale-up.

METHODS

Adolescents attending South African schools in 2012 were included in the semi-Markov running annual cycles. The ART and HIV counseling and testing program [comparator] was weighed against the interventions [viz. HIV vaccine, a dual vaccine strategy [HIV and HPV vaccines], oral pre-exposure prophylaxis [PrEP] and voluntary medical male circumcision [VMMC]; and various combinations thereof. Quality-adjusted life years [QALY] determined changes in HIV associated mortality and infections averted. One-way and probabilistic sensitivity analysis determined parameter uncertainty. Discount rates of 3% with a lifetime horizon [70 years] were applied.

RESULTS

Dual vaccination was highly cost-effective strategy [US$ 7 per QALY gained] and averted 29% of new HIV infections. VMMC [US$ 30 per QALY gained] proved more cost-effective than HIV vaccination alone [US$ 93 per QALY gained], though VMMC averted 6% more new infections than the HIV vaccine when considered among male participants. PrEP interventions were the least cost-effective with pharmaceutical and human resource spending driving the costs. Combined dual vaccination and VMMC strategies were a dominant intervention. Strategies involving PrEP were the least cost-effective.

CONCLUSION

VMMC, HIV vaccination and dual vaccination strategies were more cost-effective than any PrEP strategies. A multi-intervention biomedical approach could avert considerable new HIV infections and present a cost-effective use of resources; particularly where large scale multi-interventional randomized controlled trials are absent.

Optimum resource allocation to reduce HIV incidence across sub-Saharan Africa: a mathematical modelling study

BACKGROUND

Advances in HIV prevention methods offer promise to accelerate declines in incidence, but how these methods can be deployed to have the best effect on the heterogeneous landscape and drivers of the pandemic remains unclear. We postulated that use of epidemic heterogeneity to inform the allocation of resources for combination HIV prevention could enhance the impact of HIV funding across sub-Saharan Africa.

METHODS

We developed a compartmental mathematical model of HIV transmission and disease progression by risk group to subnational resolution in 18 countries, capturing 80% of the adult HIV burden in sub-Saharan Africa. Adults aged 15-49 years were grouped by risk of HIV acquisition and transmission, and those older than 50 years were assumed to have negligible risk. For each top-level administrative division, we calibrated the model to historical data for HIV prevalence, sexual behaviours, treatment scale-up, and demographics. We then evaluated four strategies for allocation of prevention funding over a 15 year period from 2016 to 2030, which exploited epidemic differences between subnational regions to varying degrees.

FINDINGS

For a $US20 billion representative expenditure over the 15 year period, scale-up of prevention along present funding channels could avert 5·3 million infections relative to no scale-up. Prioritisation of key populations could avert 3·7 million more infections than present funding channels, and additional prioritisation by within-country geography could avert 400 000 more infections. Removal of national constraints could avert a further 600 000 infections. Risk prioritisation has greater marginal impact than geographical prioritisation across multiple expenditure levels. However, targeting by both risk and geography is best for total impact and could achieve gains of up to three times more than present channels. A shift from the present pattern to the optimum pattern would rebalance resources towards more cost-effective interventions and emerging epidemics.

INTERPRETATION

If domestic and international funders were to align strategically to build an aggregate funding pattern that is guided by the epidemiology of HIV, and particularly by the emerging understanding of local dynamics and epidemic drivers, more cost-effective and impactful HIV prevention investments could be achieved across sub-Saharan Africa.

FUNDING

The Bill & Melinda Gates Foundation.

Prospects for HIV control in South Africa: a model-based analysis

Background

The goal of virtual elimination of horizontal and mother-to-child HIV transmission in South Africa (SA) has been proposed, but there have been few systematic investigations of which interventions are likely to be most critical to reducing HIV incidence.

Objective

This study aims to evaluate SA's potential to achieve virtual elimination targets and to identify which interventions will be most critical to achieving HIV incidence reductions.

Design

A mathematical model was developed to simulate the population-level impact of different HIV interventions in SA. Probability distributions were specified to represent uncertainty around 32 epidemiological parameters that could be influenced by interventions, and correlation coefficients (r) were calculated to assess the sensitivity of the adult HIV incidence rates and mother-to-child transmission rates (2015–2035) to each epidemiological parameter.

Results

HIV incidence in SA adults (ages 15–49) is expected to decline from 1.4% in 2011–2012 to 0.29% by 2035 (95% CI: 0.10–0.62%). The parameters most strongly correlated with future adult HIV incidence are the rate of viral suppression after initiating antiretroviral treatment (ART) (r=−0.56), the level of condom use in non-marital relationships (r=−0.40), the phase-in of intensified risk-reduction counselling for HIV-positive adults (r=0.29), the uptake of medical male circumcision (r=−0.24) and the phase-in of universal ART eligibility (r=0.22). The paediatric HIV parameters most strongly associated with mother-to-child transmission rates are the relative risk of transmission through breastfeeding when the mother is receiving ART (r=0.70) and the rate of ART initiation during pregnancy (r=−0.16).

Conclusions

The virtual elimination target of a 0.1% incidence rate in adults will be difficult to achieve. Interventions that address the infectiousness of patients after ART initiation will be particularly critical to achieving long-term HIV incidence declines in South Africa.

Dynamic Transmission Economic Evaluation of Infectious Disease Interventions in Low- and Middle-Income Countries: A Systematic Literature Review

Economic evaluation using dynamic transmission models is important for capturing the indirect effects of infectious disease interventions. We examine the use of these methods in low- and middle-income countries, where infectious diseases constitute a major burden. This review is comprised of two parts: (1) a summary of dynamic transmission economic evaluations across all disease areas published between 2011 and mid-2014 and (2) an in-depth review of mosquito-borne disease studies focusing on health economic methods and reporting. Studies were identified through a systematic search of the MEDLINE database and supplemented by reference list screening. Fifty-seven studies were eligible for inclusion in the all-disease review. The most common subject disease was HIV/AIDS, followed by malaria. A diverse range of modelling methods, outcome metrics and sensitivity analyses were used, indicating little standardisation. Seventeen studies were included in the mosquito-borne disease review. With notable exceptions, most studies did not employ economic evaluation methods beyond calculating a cost-effectiveness ratio or net benefit. Many did not adhere to health care economic evaluations reporting guidelines, particularly with respect to full model reporting and uncertainty analysis. We present a summary of the state-of-the-art and offer recommendations for improved implementation and reporting of health economic methods in this crossover discipline.

HIV Treatment and Prevention: A Simple Model to Determine Optimal Investment

OBJECTIVE

To create a simple model to help public health decision makers determine how to best invest limited resources in HIV treatment scale-up and prevention.

METHOD

A linear model was developed for determining the optimal mix of investment in HIV treatment and prevention, given a fixed budget. The model incorporates estimates of secondary health benefits accruing from HIV treatment and prevention and allows for diseconomies of scale in program costs and subadditive benefits from concurrent program implementation. Data sources were published literature. The target population was individuals infected with HIV or at risk of acquiring it. Illustrative examples of interventions include preexposure prophylaxis (PrEP), community-based education (CBE), and antiretroviral therapy (ART) for men who have sex with men (MSM) in the US. Outcome measures were incremental cost, quality-adjusted life-years gained, and HIV infections averted.

RESULTS

Base case analysis indicated that it is optimal to invest in ART before PrEP and to invest in CBE before scaling up ART. Diseconomies of scale reduced the optimal investment level. Subadditivity of benefits did not affect the optimal allocation for relatively low implementation levels. The sensitivity analysis indicated that investment in ART before PrEP was optimal in all scenarios tested. Investment in ART before CBE became optimal when CBE reduced risky behavior by 4% or less. Limitations of the study are that dynamic effects are approximated with a static model.

CONCLUSIONS

Our model provides a simple yet accurate means of determining optimal investment in HIV prevention and treatment. For MSM in the US, HIV control funds should be prioritized on inexpensive, effective programs like CBE, then on ART scale-up, with only minimal investment in PrEP.

Cost effectiveness of option B plus for prevention of mother-to-child transmission of HIV in resource-limited countries: evidence from Kumasi, Ghana

BACKGROUND

Achieving the goal of eliminating mother-to-child HIV transmission (MTCT) necessitates increased access to antiretroviral therapy (ART) for HIV-infected pregnant women. Option B provides ART through pregnancy and breastfeeding, whereas Option B+ recommends continuous ART regardless of CD4 count, thus potentially reducing MTCT during future pregnancies. Our objective was to compare maternal and pediatric health outcomes and cost-effectiveness of Option B+ versus Option B in Ghana.

METHODS

A decision-analytic model was developed to simulate HIV progression in mothers and transmission (in utero, during birth, or through breastfeeding) to current and all future children. Clinical parameters, including antenatal care access and fertility rates, were estimated from a retrospective review of 817 medical records at two hospitals in Ghana. Additional parameters were obtained from published literature. Modeled outcomes include HIV infections averted among newborn children, quality-adjusted life-years (QALYs), and cost-effectiveness ratios.

RESULTS

HIV-infected women in Ghana have a lifetime average of 2.3 children (SD 1.3). Projected maternal life expectancy under Option B+ is 16.1 years, versus 16.0 years with Option B, yielding a gain of 0.1 maternal QALYs and 3.2 additional QALYs per child. Despite higher initial ART costs, Option B+ costs $785/QALY gained, a value considered very cost-effective by World Health Organization benchmarks. Widespread implementation of Option B+ in Ghana could theoretically prevent up to 668 HIV infections among children annually. Cost-effectiveness estimates remained favorable over robust sensitivity analyses.

CONCLUSIONS

Although more expensive than Option B, Option B+ substantially reduces MTCT in future pregnancies, increases both maternal and pediatric QALYs, and is a cost-effective use of limited resources in Ghana.

Modelling challenges in context: lessons from malaria, HIV, and tuberculosis

Malaria, HIV, and tuberculosis (TB) collectively account for several million deaths each year, with all three ranking among the top ten killers in low-income countries. Despite being caused by very different organisms, malaria, HIV, and TB present a suite of challenges for mathematical modellers that are particularly pronounced in these infections, but represent general problems in infectious disease modelling, and highlight many of the challenges described throughout this issue. Here, we describe some of the unifying challenges that arise in modelling malaria, HIV, and TB, including variation in dynamics within the host, diversity in the pathogen, and heterogeneity in human contact networks and behaviour. Through the lens of these three pathogens, we provide specific examples of the other challenges in this issue and discuss their implications for informing public health efforts.

Male circumcision for protection against HIV infection in sub-Saharan Africa: the evidence in favour justifies the implementation now in progress

This article responds to a recent 'controversy study' in Global Public Health by de Camargo et al. directed at three randomised controlled trials (RCTs) of male circumcision (MC) for HIV prevention. These trials were conducted in three countries in sub-Saharan Africa (SSA) and published in 2005 and 2007. The RCTs confirmed observational data that had accumulated over the preceding two decades showing that MC reduces by 60% the risk of HIV infection in heterosexual men. Based on the RCT results, MC was adopted by global and national HIV policy-makers as an additional intervention for HIV prevention. Voluntary medical MC (VMMC) is now being implemented in 14 SSA countries. Thus referring to MC for HIV prevention as 'debate' and viewing MC through a lens of controversy seems mistaken. In their criticism, de Camargo et al. misrepresent and misinterpret current science supporting MC for HIV prevention, omit previous denunciations of arguments similar to theirs, and ignore evidence from ongoing scientific research. Here we point out the flaws in three areas de Camargo et al. find contentious. In doing so, we direct readers to growing evidence of MC as an efficacious, safe, acceptable, relatively low-cost one-off biomedical intervention for HIV prevention.

Reprint of: "This is the medicine:" a Kenyan community responds to a sexual concurrency reduction intervention

We report the results of the first study designed to evaluate the feasibility and acceptability of an HIV prevention intervention focused on concurrent sexual partnerships. Mathematical models and longitudinal studies of stable couples indicate concurrency plays a critical role in sustaining generalized HIV epidemics in heterosexual populations, and East and Southern African nations identified concurrency reduction as a priority for HIV prevention. "Know Your Network" (KYN) is a single-session community-level concurrency awareness intervention designed to address this need. It is rooted in traditional social network research, but takes advantage of new network methodology and years of participatory action research with communities living in a region of Kenya with the highest HIV prevalence nationally. KYN combines didactic presentation, interactive exercises, high-impact graphics, and a network survey with immediate visualization of the results, to prompt a community conversation about sexual norms. We combined focus group discussions and the traditional east African baraza to evaluate the feasibility and acceptability of KYN for use with adults living in rural Nyanza Province, Kenya. We were able to implement KYN with fidelity to its components. Participants understood the intervention's messages about concurrency and its role in HIV transmission through sexual networks. They agreed to provide anonymous egocentric data on their sexual partnerships, and in return we successfully simulated a representation of their local network for them to view and discuss. This launched a dynamic conversation about concurrency and sexual norms that persisted after the intervention. The concurrency message was novel, but resonant to participants, who reported sharing it with their children, friends, and sexual partners. With clear evidence of KYN's feasibility and acceptability, it would be appropriate to evaluate the effectiveness of the intervention using a community-randomized trial. If effective, KYN would offer an inexpensive complement to ongoing comprehensive HIV prevention efforts in generalized epidemic settings.

HIV prevention in clinical care settings: 2014 recommendations of the International Antiviral Society-USA Panel

IMPORTANCE

Emerging data warrant the integration of biomedical and behavioral recommendations for human immunodeficiency virus (HIV) prevention in clinical care settings.

OBJECTIVE

To provide current recommendations for the prevention of HIV infection in adults and adolescents for integration in clinical care settings.

DATA SOURCES, STUDY SELECTION, AND DATA SYNTHESIS

Data published or presented as abstracts at scientific conferences (past 17 years) were systematically searched and reviewed by the International Antiviral (formerly AIDS) Society-USA HIV Prevention Recommendations Panel. Panel members supplied additional relevant publications, reviewed available data, and formed recommendations by full-panel consensus.

RESULTS

Testing for HIV is recommended at least once for all adults and adolescents, with repeated testing for those at increased risk of acquiring HIV. Clinicians should be alert to the possibility of acute HIV infection and promptly pursue diagnostic testing if suspected. At diagnosis of HIV, all individuals should be linked to care for timely initiation of antiretroviral therapy (ART). Support for adherence and retention in care, individualized risk assessment and counseling, assistance with partner notification, and periodic screening for common sexually transmitted infections (STIs) is recommended for HIV-infected individuals as part of care. In HIV-uninfected patients, those persons at high risk of HIV infection should be prioritized for delivery of interventions such as preexposure prophylaxis and individualized counseling on risk reduction. Daily emtricitabine/tenofovir disoproxil fumarate is recommended as preexposure prophylaxis for persons at high risk for HIV based on background incidence or recent diagnosis of incident STIs, use of injection drugs or shared needles, or recent use of nonoccupational postexposure prophylaxis; ongoing use of preexposure prophylaxis should be guided by regular risk assessment. For persons who inject drugs, harm reduction services should be provided (needle and syringe exchange programs, supervised injection, and available medically assisted therapies, including opioid agonists and antagonists); low-threshold detoxification and drug cessation programs should be made available. Postexposure prophylaxis is recommended for all persons who have sustained a mucosal or parenteral exposure to HIV from a known infected source and should be initiated as soon as possible.

CONCLUSIONS AND RELEVANCE

Data support the integration of biomedical and behavioral approaches for prevention of HIV infection in clinical care settings. A concerted effort to implement combination strategies for HIV prevention is needed to realize the goal of an AIDS-free generation.

HIV epidemic control-a model for optimal allocation of prevention and treatment resources

With 33 million people living with human immunodeficiency virus (HIV) worldwide and 2.7 million new infections occurring annually, additional HIV prevention and treatment efforts are urgently needed. However, available resources for HIV control are limited and must be used efficiently to minimize the future spread of the epidemic. We develop a model to determine the appropriate resource allocation between expanded HIV prevention and treatment services. We create an epidemic model that incorporates multiple key populations with different transmission modes, as well as production functions that relate investment in prevention and treatment programs to changes in transmission and treatment rates. The goal is to allocate resources to minimize R 0, the reproductive rate of infection. We first develop a single-population model and determine the optimal resource allocation between HIV prevention and treatment. We extend the analysis to multiple independent populations, with resource allocation among interventions and populations. We then include the effects of HIV transmission between key populations. We apply our model to examine HIV epidemic control in two different settings, Uganda and Russia. As part of these applications, we develop a novel approach for estimating empirical HIV program production functions. Our study provides insights into the important question of resource allocation for a country's optimal response to its HIV epidemic and provides a practical approach for decision makers. Better decisions about allocating limited HIV resources can improve response to the epidemic and increase access to HIV prevention and treatment services for millions of people worldwide.

"This is the medicine:" A Kenyan community responds to a sexual concurrency reduction intervention

We report the results of the first study designed to evaluate the feasibility and acceptability of an HIV prevention intervention focused on concurrent sexual partnerships. Mathematical models and longitudinal studies of stable couples indicate concurrency plays a critical role in sustaining generalized HIV epidemics in heterosexual populations, and East and Southern African nations identified concurrency reduction as a priority for HIV prevention. "Know Your Network" (KYN) is a single-session community-level concurrency awareness intervention designed to address this need. It is rooted in traditional social network research, but takes advantage of new network methodology and years of participatory action research with communities living in a region of Kenya with the highest HIV prevalence nationally. KYN combines didactic presentation, interactive exercises, high-impact graphics, and a network survey with immediate visualization of the results, to prompt a community conversation about sexual norms. We combined focus group discussions and the traditional east African baraza to evaluate the feasibility and acceptability of KYN for use with adults living in rural Nyanza Province, Kenya. We were able to implement KYN with fidelity to its components. Participants understood the intervention's messages about concurrency and its role in HIV transmission through sexual networks. They agreed to provide anonymous egocentric data on their sexual partnerships, and in return we successfully simulated a representation of their local network for them to view and discuss. This launched a dynamic conversation about concurrency and sexual norms that persisted after the intervention. The concurrency message was novel, but resonant to participants, who reported sharing it with their children, friends, and sexual partners. With clear evidence of KYN's feasibility and acceptability, it would be appropriate to evaluate the effectiveness of the intervention using a community-randomized trial. If effective, KYN would offer an inexpensive complement to ongoing comprehensive HIV prevention efforts in generalized epidemic settings.

Expanded HIV testing in low-prevalence, high-income countries: a cost-effectiveness analysis for the United Kingdom

Objective

In many high-income countries with low HIV prevalence, significant numbers of persons living with HIV (PLHIV) remain undiagnosed. Identification of PLHIV via HIV testing offers timely access to lifesaving antiretroviral therapy (ART) and decreases HIV transmission. We estimated the effectiveness and cost-effectiveness of HIV testing in the United Kingdom (UK), where 25% of PLHIV are estimated to be undiagnosed.

Design

We developed a dynamic compartmental model to analyze strategies to expand HIV testing and treatment in the UK, with particular focus on men who have sex with men (MSM), people who inject drugs (PWID), and individuals from HIV-endemic countries.

Methods

We estimated HIV prevalence, incidence, quality-adjusted life years (QALYs), and health care costs over 10 years, and cost-effectiveness.

Results

Annual HIV testing of all adults could avert 5% of new infections, even with no behavior change following HIV diagnosis because of earlier ART initiation, or up to 18% if risky behavior is halved. This strategy costs £67,000–£106,000/QALY gained. Providing annual testing only to MSM, PWID, and people from HIV-endemic countries, and one-time testing for all other adults, prevents 4–15% of infections, requires one-fourth as many tests to diagnose each PLHIV, and costs £17,500/QALY gained. Augmenting this program with increased ART access could add 145,000 QALYs to the population over 10 years, at £26,800/QALY gained.

Conclusions

Annual HIV testing of key populations in the UK is very cost-effective. Additional one-time testing of all other adults could identify the majority of undiagnosed PLHIV. These findings are potentially relevant to other low-prevalence, high-income countries.

Cost-effectiveness of a package of interventions for expedited antiretroviral therapy initiation during pregnancy in Cape Town, South Africa

Initiating antiretroviral therapy (ART) early in pregnancy is an important component of effective interventions to prevent the mother-to-child transmission of HIV (PMTCT). The rapid initiation of ART in pregnancy(RAP) program was a package of interventions to expedite ART initiation in pregnant women in Cape Town, South Africa. Retrospective cost-effectiveness, sensitivity and threshold analyses were conducted of the RAP program to determine the cost-utility thresholds for rapid initiation of ART in pregnancy. Costs were drawn from a detailed micro-costing of the program. The overall programmatic cost was US$880 per woman and the base case cost-effectiveness ratio was US$1,160 per quality-adjusted lifeyear (QALY) saved. In threshold analyses, the RAP program remained cost-effective if mother-to-child transmission was reduced by C0.33 %; if C1.76 QALY were saved with each averted perinatal infection; or if RAP-related costs were under US$4,020 per woman. The package of rapid initiation services was very cost-effective, as compared to standard services in this setting. Threshold analyses demonstrated that the intervention required minimal reductions in perinatal infections in order to be cost-effective. Interventions for the rapid initiation of ART in pregnancy hold considerable potential as a cost-effective use of limited resources for PMTCT in sub-Saharan Africa.

Effectiveness and cost effectiveness of oral pre-exposure prophylaxis in a portfolio of prevention programs for injection drug users in mixed HIV epidemics

Background

Pre-exposure prophylaxis with oral antiretroviral treatment (oral PrEP) for HIV-uninfected injection drug users (IDUs) is potentially useful in controlling HIV epidemics with a significant injection drug use component. We estimated the effectiveness and cost effectiveness of strategies for using oral PrEP in various combinations with methadone maintenance treatment (MMT) and antiretroviral treatment (ART) in Ukraine, a representative case for mixed HIV epidemics.

Methods and Findings

We developed a dynamic compartmental model of the HIV epidemic in a population of non-IDUs, IDUs who inject opiates, and IDUs in MMT, adding an oral PrEP program (tenofovir/emtricitabine, 49% susceptibility reduction) for uninfected IDUs. We analyzed intervention portfolios consisting of oral PrEP (25% or 50% of uninfected IDUs), MMT (25% of IDUs), and ART (80% of all eligible patients). We measured health care costs, quality-adjusted life years (QALYs), HIV prevalence, HIV infections averted, and incremental cost effectiveness. A combination of PrEP for 50% of IDUs and MMT lowered HIV prevalence the most in both IDUs and the general population. ART combined with MMT and PrEP (50% access) averted the most infections (14,267). For a PrEP cost of $950, the most cost-effective strategy was MMT, at $520/QALY gained versus no intervention. The next most cost-effective strategy consisted of MMT and ART, costing $1,000/QALY gained compared to MMT alone. Further adding PrEP (25% access) was also cost effective by World Health Organization standards, at $1,700/QALY gained. PrEP alone became as cost effective as MMT at a cost of $650, and cost saving at $370 or less.

Conclusions

Oral PrEP for IDUs can be part of an effective and cost-effective strategy to control HIV in regions where injection drug use is a significant driver of the epidemic. Where budgets are limited, focusing on MMT and ART access should be the priority, unless PrEP has low cost.

Combination HIV prevention: the value and interpretation of mathematical models

Mathematical models of HIV prevention interventions often provide critical insights related to programmatic design and economic efficiency. One recent dynamic model by Long et al. highlights that a combination prevention approach - with testing, treatment, circumcision, microbicides and PrEP - may decrease transmissions by over 60% and may be very cost-effective in South Africa. In this analysis, the authors introduce the critical concept of joint effectiveness of preventions programs and demonstrate how some programs operate synergistically (HIV screening coupled with early treatment) while others may create redundancies (microbicides coupled with pre-exposure prophylaxis). Whether combination HIV prevention programs perform with additive, multiplicative or maximal effectiveness will be important to consider in anticipation of their combined transmission impact.