Measuring HIV Acquisitions Among Partners of Key Populations: Estimates From HIV Transmission Dynamic Models.

BACKGROUND: Key populations (KPs), including female sex workers (FSWs), gay men and other men who have sex with men (MSM), people who inject drugs (PWID), and transgender women (TGW) experience disproportionate risks of HIV acquisition. The UNAIDS Global AIDS 2022 Update reported that one-quarter of all new HIV infections occurred among their non-KP sexual partners. However, this fraction relied on heuristics regarding the ratio of new infections that KPs transmitted to their non-KP partners to the new infections acquired among KPs (herein referred to as "infection ratios"). We recalculated these ratios using dynamic transmission models. SETTING: One hundred seventy-eight settings (106 countries). METHODS: Infection ratios for FSW, MSM, PWID, TGW, and clients of FSW were estimated from 12 models for 2020. RESULTS: Median model estimates of infection ratios were 0.7 (interquartile range: 0.5-1.0; n = 172 estimates) and 1.2 (0.8-1.8; n = 127) for acquisitions from FSW clients and transmissions from FSW to all their non-KP partners, respectively, which were comparable with the previous UNAIDS assumptions (0.2-1.5 across regions). Model estimates for female partners of MSM were 0.5 (0.2-0.8; n = 20) and 0.3 (0.2-0.4; n = 10) for partners of PWID across settings in Eastern and Southern Africa, lower than the corresponding UNAIDS assumptions (0.9 and 0.8, respectively). The few available model estimates for TGW were higher [5.1 (1.2-7.0; n = 8)] than the UNAIDS assumptions (0.1-0.3). Model estimates for non-FSW partners of FSW clients in Western and Central Africa were high (1.7; 1.0-2.3; n = 29). CONCLUSIONS: Ratios of new infections among non-KP partners relative to KP were high, confirming the importance of better addressing prevention and treatment needs among KP as central to reducing overall HIV incidence.

The AIDS Epidemic Model 2023 for Estimating HIV Trends and Transmission Dynamics in Asian Epidemic Settings.

BACKGROUND: Thirteen Asian countries use the AIDS Epidemic Model (AEM) as their HIV model of choice. This article describes AEM, its inputs, and its application to national modeling. SETTING: AEM is an incidence tool used by Spectrum for the Joint United Nations Programme on HIV/AIDS global estimates process. METHODS: AEM simulates transmission of HIV among key populations (KPs) using measured trends in risk behaviors. The inputs, structure and calculations, interface, and outputs of AEM are described. The AEM process includes (1) collating and synthesizing data on KP risk behaviors, epidemiology, and size to produce model input trends; (2) calibrating the model to observed HIV prevalence; (3) extracting outputs by KP to describe epidemic dynamics and assist in improving responses; and (4) importing AEM incidence into Spectrum for global estimates. Recent changes to better align AEM mortality with Spectrum and add preexposure prophylaxis are described. RESULTS: The application of AEM in Thailand is presented, describing the outputs and uses in-country. AEM replicated observed epidemiological trends when given observed behavioral inputs. The strengths and limitations of AEM are presented and used to inform thoughts on future directions for global models. CONCLUSIONS: AEM captures regional HIV epidemiology well and continues to evolve to meet country and global process needs. The addition of time-varying mortality and progression parameters has improved the alignment of the key population compartmental model of AEM with the age-sex-structured national model of Spectrum. Many of the features of AEM, including tracking the sources of infections over time, should be incorporated in future global efforts to build more generalizable models to guide policy and programs.

Evolving HIV epidemics: the urgent need to refocus on populations with risk.

PURPOSE OF REVIEW: To explore the comparative importance of HIV infections among key populations and their intimate partners as HIV epidemics evolve, and to review implications for guiding responses. RECENT FINDINGS: Even as concentrated epidemics evolve, new infections among current and former key population members and their intimate partners dominate new infections. Prevalent infections in the general population grow primarily because of key population turnover and infections among their intimate partners. In generalized epidemic settings, data and analysis on key populations are often inadequate to assess the impact of key population-focused responses, so they remain limited in coverage and under resourced. Models must incorporate downstream infections in comparing impacts of alternative responses. SUMMARY: Recognize that every epidemic is unique, moving beyond the overly simplistic concentrated/generalized epidemic paradigm that can misdirect resources. Guide HIV responses by gathering and using locally relevant data, understanding risk heterogeneity, and applying modeling at both national and sub-national levels to optimize resource allocations among different populations for greatest impact. Translate this improved understanding into clear, unequivocal advice for policymakers on where to focus for impact, breaking them free of the generalized/concentrated paradigm limiting their thinking and affecting their decisions.

Updates to the Spectrum/Estimations and Projections Package model for estimating trends and current values for key HIV indicators.

BACKGROUND: The Spectrum model is used by national programs and UNAIDS to prepare annual estimates of the status of the HIV epidemic in 160 countries. The model and assumptions are updated regularly under the guidance of the UNAIDS Reference Group on Estimates, Modelling and Projections in response to new data, studies, and program needs. This study describes the most recent updates for the 2016 round of estimates. METHODS: Meetings of the UNAIDS Reference Group include individuals with extensive knowledge of HIV programs, research, statistics, and public policy. The Reference Group also collaborates with other institutions (such as the United Nations Population Division and the US Census Bureau) and projects (such as the ALPHA Network and IeDEA Consortium) to ensure that latest methods and data are used in the preparation of the annual estimates. In the past year new methods and data have been introduced for pediatric estimates, incidence fitting, and ART mortality (described elsewhere in this supplement). RESULTS: The 2016 version of Spectrum includes a number of other enhancements, including updated demographic data from the United Nations Population Division, program options for treatment (treat all), and programs to prevent mother-to-child transmission (option B+), improved methods to aggregate uncertainty to regional and global levels, several options for generating incidence trends, adjustments to the Estimations and Projections Package model to better incorporate aging effects, adjustments to account for the changing bias in prevalence from antenatal clinic surveillance, and an option to fit incidence among all adults 15+ in addition to 15-49. CONCLUSION: The new methods and data implemented in the 2016 version of Spectrum allow national programs more flexibility in describing their programs and improve the estimates of key indicators and their uncertainty.

The impact of Thailand's public health response to the HIV epidemic 1984-2015: understanding the ingredients of success.

INTRODUCTION: Thailand has been heralded as a global leader in HIV prevention and treatment, and its experience with the HIV/AIDS epidemic holds valuable lessons for public health. This paper documents Thailand's response to its HIV epidemic from the late 1980s until today, and analyses its epidemiological impact (incidence and mortality). We discuss the association between the trajectory of HIV incidence and mortality rates over time, and the programmatic investments, policies and interventions that were implemented in the last three decades. METHODS: This is a review paper that draws on published literature, unpublished sources and routine behavioural and serological surveillance data since 1989. It is informed by the modelling of epidemiological impacts using the AIDS Epidemic Model. The AIDS Epidemic Model and Spectrum were used to assess the impact on incidence and mortality. Apart from epidemiological data, National AIDS Spending Assessment and programme data were also used to assess financial investments. RESULTS: Thailand is well on its way to meeting the 90-90-90 targets, the goal that by 2020, 90% of people living with HIV know their HIV status, 90% of people with diagnosed HIV infection receive sustained antiretroviral therapy, and 90% of people receiving antiretroviral therapy (ART) are virally suppressed. In Thailand, 89% of people living with HIV know their status, 72% receive ART and 82% have viral load testing - 99% of whom are suppressed. The public health response to HIV in Thailand has averted 5.7 million infections since 1991. If Thailand had not responded in 1991 to the HIV epidemic, and had there been no prevention and ART provision, the country would have experienced an estimated 158,000-225,000 deaths in the 2001-2006 period. This figure would have risen to 231,000-268,924 in the 2007-2014 period. A total of 196,000 deaths were averted between 2001 and 2014. If ART scale-up had not occurred in 2001, Thailand would have experienced between 50,000 and 55,000 deaths per year in the period 2001-2006, and 31,000-46,000 annual deaths between 2007 and 2014. The main impact in terms of deaths averted is seen from 2004 onwards, reflecting treatment scale up. CONCLUSIONS: Thailand's AIDS response has prevented needless morbidity and mortality due to the HIV epidemic. In the context of Thailand's ageing population, it is faced with the twin challenges of maintaining life-long quality services among HIV patients and sustaining behaviour change to maintain primary prevention gains. Keeping the focus of the policy makers and health administrators on 'Ending the HIV epidemic' will require consistent advocacy, and evidence-based, innovative and efficient approaches.

Is a HIV vaccine a viable option and at what price? An economic evaluation of adding HIV vaccination into existing prevention programs in Thailand.

BACKGROUND: This study aims to determine the maximum price at which HIV vaccination is cost-effective in the Thai healthcare setting. It also aims to identify the relative importance of vaccine characteristics and risk behavior changes among vaccine recipients to determine how they affect this cost-effectiveness. METHODS: A semi-Markov model was developed to estimate the costs and health outcomes of HIV prevention programs combined with HIV vaccination in comparison to the existing HIV prevention programs without vaccination. The estimation was based on a lifetime horizon period (99 years) and used the government perspective. The analysis focused on both the general population and specific high-risk population groups. The maximum price of cost-effective vaccination was defined by using threshold analysis; one-way and probabilistic sensitivity analyses were performed. The study employed an expected value of perfect information (EVPI) analysis to determine the relative importance of parameters and to prioritize future studies. RESULTS: The most expensive HIV vaccination which is cost-effective when given to the general population was 12,000 Thai baht (US$1 = 34 Thai baht in 2009). This vaccination came with 70% vaccine efficacy and lifetime protection as long as risk behavior was unchanged post-vaccination. The vaccine would be considered cost-ineffective at any price if it demonstrated low efficacy (30%) and if post-vaccination risk behavior increased by 10% or more, especially among the high-risk population groups. The incremental cost-effectiveness ratios were the most sensitive to change in post-vaccination risk behavior, followed by vaccine efficacy and duration of protection. The EVPI indicated the need to quantify vaccine efficacy, changed post-vaccination risk behavior, and the costs of vaccination programs. CONCLUSIONS: The approach used in this study differentiated it from other economic evaluations and can be applied for the economic evaluation of other health interventions not available in healthcare systems. This study is important not only for researchers conducting future HIV vaccine research but also for policy decision makers who, in the future, will consider vaccine adoption.

HIV transmission rates in Thailand: evidence of HIV prevention and transmission decline.

BACKGROUND: Analysis of HIV transmission rates has provided insight into the impacts of HIV-related prevention programming and policies in the United States by providing timely information beyond incidence or prevalence alone. The purpose of this analysis is to use transmission rates to assess past prevention efforts and explore trends of the epidemic in subpopulations within Thailand. METHODS: Asian Epidemic Model HIV incidence and prevalence were used to calculate transmission rates over time nationally and among high-risk populations. RESULTS: A national HIV/AIDS program implemented in Thailand in the 1990s that targeted sex workers and the general population was correlated with a decrease in new cases despite high prevalence. The turning point of the epidemic was in 1991 when the national transmission rate was 32%. By the late 1990s, the rate dropped to less than 4%. All subpopulations experienced a rate decline; however, sex workers still experienced higher transmission rates. CONCLUSIONS: The declining trend in HIV transmission rates despite ever-growing prevalence indicates prevention success correlated with the national HIV/AIDS program. Data from subgroup analyses provide stronger evidence of prevention success than incidence alone, as this measure demonstrates the effect of efforts and accounts for the burden of disease in the population.

The economics of effective AIDS treatment in Thailand.

INTRODUCTION: The speed with which Thailand has scaled up public provision of antiretroviral therapy (ART) has been unprecedented, with more than 80 000 individuals on treatment at the end of 2006 through Thailand's National Access to Antiretroviral Program for People Living with HIV/AIDS (NAPHA). This paper projects the cost effectiveness, the affordability and the future fiscal burden of NAPHA to the government of Thailand under several different policy scenarios until the year 2025. METHODS: An economic/epidemiological model of access to ART was constructed, and this composite model was calibrated to economic and epidemiological data from Thailand and other countries. The economic model adopts the conditional logit specification of demand allocation across multiple treatment modes, and the epidemiological model is a deterministic difference-equation model fitted to the cumulated data on HIV incidence in each risk group. RESULTS: The paper estimates that under 2005 prices NAPHA will save life-years at approximately US$736 per life-year saved with first-line drugs alone and for approximately US$2145 per life-year if second-line drugs are included. Enhancing NAPHA with policies to recruit patients soon after they are first eligible for ART or to enhance their adherence would raise the cost per life-year saved, but the cost would be small per additional life-year saved, and is therefore justifiable. The fiscal burden of a policy including second as well as first-line drugs would be substantial, rising to 23% of the total health budget by 2014, but the authors judge this cost to be affordable given Thailand's strong overall economic performance. The paper estimates that a 90% reduction in the future cost of second-line therapy by the exercise of Thailand's World Trade Organization authority to issue compulsory licences would save the government approximately US$3.2 billion to 2025 and reduce the cost of NAPHA per life-year saved from US$2145 to approximately US$940.