Increasing sexual risk behaviour among Dutch men who have sex with men: mathematical models versus prospective cohort data

Diverging trends in incidence of HIV versus other sexually transmitted infections in HIV-negative MSM in Amsterdam

OBJECTIVES

We investigated changes in incidence rates of HIV and sexually transmitted infections (STIs) and trends in sexual behavior in MSM from 2009 to 2017.

DESIGN

Open prospective cohort study.

METHODS

HIV-negative MSM enrolled in the Amsterdam Cohort Studies were included. Participants semiannually completed a questionnaire on sexual behavior and were tested for HIV-1, syphilis, and urethral, anal and pharyngeal chlamydia and gonorrhea. Time trends in incidence rates were analyzed using exponential survival models.

RESULTS

During follow-up, 42 of 905 MSM acquired HIV. The HIV incidence rate was 1.9/100 person-years [95% confidence interval (CI) 1.0-3.7] in 2009 and decreased to 0.5/100 person-years (95% CI 0.2-1.4) in 2017 (P = 0.03). The largest decrease was observed in participants aged at least 35 years (P = 0.005), while the trend remained stable in 18-34 year olds (P = 0.4). The incidence rate for any bacterial STI was 16.8/100 person-years (95% CI 13.4-21.0) in 2010, and increased to 33.1/100 person-years (95% CI 29.0-37.9) in 2017 (P < 0.001). Between 2009 and 2017, the percentage reporting condomless anal sex with casual partners increased from 26.9 to 39.4% (P < 0.001), and the mean number of casual partners from eight (95% CI 8-8) to 11 (95% CI 10-11) (P = 0.05). Condomless anal sex with steady partner(s) remained stable over time (P = 0.5).

CONCLUSION

Among MSM in Amsterdam, incidence rates of HIV versus other STI show diverging trends. The increase in STI incidence coincides with a decrease in condom use with casual partners. The decrease in HIV incidence, despite increased sexual risk behavior, suggests that other HIV prevention methods have been successful in reducing HIV transmission among MSM.

Implications for a policy of initiating antiretroviral therapy in people diagnosed with human immunodeficiency virus: the CAPRA research programme

Background

More than 100,000 people in the UK are living with a human immunodeficiency virus (HIV) infection. There are currently estimated to be around 4000 people newly infected in the UK per year, mostly men who have sex with men (MSM). It has become increasingly clear that antiretroviral therapy (ART) used to treat people infected with HIV also has a profound effect on infectivity. At the initiation of the programme, it was the policy in the UK to initiate ART in people when their cluster of differentiation 4 (CD4) count was approaching 350/µl.

Objectives

To assess what would be the effectiveness and cost-effectiveness of a policy of immediate initiation of ART at diagnosis among MSM, taking into account the potential reductions in new infections.

Design

We calibrated an individual-based model of HIV transmission, progression and the effect of ART in MSM, informed by a series of studies on sexual behaviour in relation to ART use and the transmission risk in people with viral suppression on ART, and by surveillance data collected by Public Health England.

Setting, participants and interventions

The series of studies used to inform the model included (1) the Antiretrovirals, Sexual Transmission Risk and Attitudes (ASTRA) study, a cross-sectional self-administered questionnaire study of people diagnosed with HIV attending eight HIV outpatient clinics in the UK (2011–12); (2) the Cognitive Impairment in People with HIV in the European Region (CIPHER) study, a study of levels of neurocognitive impairment in HIV-positive ASTRA participants and people from HIV clinics in Rome, Copenhagen and Minsk; (3) the Attitudes to, and Understanding of, Risk of Acquisition of HIV (AURAH) study, a cross-sectional self-administered questionnaire study of individuals who have not been diagnosed as HIV-positive attending 20 genitourinary medicine clinics across the UK (2013–14); (4) a substudy of sexual behaviour among individuals enrolled in an open-label multicentre international randomised trial (from 2013) of immediate versus deferred ART (to CD4 cell counts of 350/µl) in people with CD4 cell counts of > 500/µl [the Strategic Timing of Antiretroviral Therapy (START) trial]; and (5) Partners of People on ART: a new Evaluation of the Risks (PARTNER), an observational multicentre longitudinal study of HIV serodifferent heterosexual and MSM couples, in which the HIV-positive partner is on ART (2010–14).

Main outcome measures

The main outcome measures were the clinical effectiveness and cost-effectiveness of a policy of immediate initiation of ART at diagnosis.

Results

Based on data from studies (i)–(v), we estimated from our modelling work that increases in condomless sex (CLS) among MSM as a whole may explain the increase in HIV infection incidence in MSM epidemics over a time when ART coverage and viral suppression increased, demonstrating the limiting effects of non-condom use on the HIV epidemic among MSM. Accordingly, an increase in the overall proportion of MSM living with HIV who are virally suppressed on ART from the current level of < 60% to 90% without increases in CLS was required to achieve a reduction in the incidence of HIV among MSM to < 1 per 1000 person-years. The incremental cost-effectiveness ratio associated with the fourfold increase in levels of HIV testing and ART at diagnosis required to provide this increase from < 60% to 90% was £20,000 if we assumed continuation of current ART prices. However, this value falls to £3500 if we assume that ART prices will fall to 20% of their current cost as a result of the introduction of generic drugs. Therefore, our evaluation suggests that ART initiation at diagnosis is likely to be highly cost-effective in MSM at a population level, particularly accounting for future lower ART costs as generic drugs are used. The impact will be much greater if levels of HIV testing can be enhanced.

Limitations

It was necessary to make some assumptions beyond the available data in order to extrapolate cost-effectiveness through modelling.

Conclusions

Our findings suggest that ART initiation at diagnosis is likely to be cost-effective in MSM. Of note, after this programme of work was completed, results from the main START trial demonstrated benefit in ART initiation even in people with CD4 cell counts of > 500/µl, supporting ART initiation in people diagnosed with a HIV infection.

Future work

There is a need for future research into the means of increasing the frequency with which MSM test for HIV.

Funding

The National Institute for Health Research Programme Grants for Applied Research programme.

Limited overlap between phylogenetic HIV and hepatitis C virus clusters illustrates the dynamic sexual network structure of Dutch HIV-infected MSM

OBJECTIVE

MSM are at increased risk for infection with HIV-1 and hepatitis C virus (HCV). Is HIV/HCV coinfection confined to specific HIV transmission networks?

DESIGN AND METHODS

A HIV phylogenetic tree was constructed for 5038 HIV-1 subtype B polymerase (pol) sequences obtained from MSM in the AIDS therapy evaluation in the Netherlands cohort. We investigated the existence of HIV clusters with increased HCV prevalence, the HIV phylogenetic density (i.e. the number of potential HIV transmission partners) of HIV/HCV-coinfected MSM compared with HIV-infected MSM without HCV, and the overlap in HIV and HCV phylogenies using HCV nonstructural protein 5B sequences from 183 HIV-infected MSM with acute HCV infection.

RESULTS

Five hundred and sixty-three of 5038 (11.2%) HIV-infected MSM tested HCV positive. Phylogenetic analysis revealed 93 large HIV clusters (≥10 MSM), 370 small HIV clusters (2-9 MSM), and 867 singletons with a median HCV prevalence of 11.5, 11.6, and 9.3%, respectively. We identified six large HIV clusters with elevated HCV prevalence (range 23.5-46.2%). Median HIV phylogenetic densities for MSM with HCV (3, interquartile range 1-7) and without HCV (3, interquartile range 1-8) were similar. HCV phylogeny showed 12 MSM-specific HCV clusters (clustersize: 2-39 HCV sequences); 12.7% of HCV infections were part of the same HIV and HCV cluster.

CONCLUSION

We observed few HIV clusters with elevated HCV prevalence, no increase in the HIV phylogenetic density of HIV/HCV-coinfected MSM compared to HIV-infected MSM without HCV, and limited overlap between HIV and HCV phylogenies among HIV/HCV-coinfected MSM. Our data do not support the existence of MSM-specific sexual networks that fuel both the HIV and HCV epidemic.

Impact of Heterogeneity in Sexual Behavior on Effectiveness in Reducing HIV Transmission with Test-and-Treat Strategy

The WHO’s early-release guideline for antiretroviral treatment (ART) of HIV infection based on a recent trial conducted in 34 countries recommends starting treatment immediately upon an HIV diagnosis. Therefore, the test-and-treat strategy may become more widely used in an effort to scale up HIV treatment and curb further transmission. Here we examine behavioural determinants of HIV transmission and how heterogeneity in sexual behaviour influences the outcomes of this strategy. Using a deterministic model, we perform a systematic investigation into the effects of various mixing patterns in a population of men who have sex with men (MSM), stratified by partner change rates, on the elimination threshold and endemic HIV prevalence. We find that both the level of overdispersion in the distribution of the number of sexual partners and mixing between population subgroups have a large influence on endemic prevalence before introduction of ART and on possible long term effectiveness of ART. Increasing heterogeneity in risk behavior may lead to lower endemic prevalence levels, but requires higher coverage levels of ART for elimination. Elimination is only feasible for populations with a rather low degree of assortativeness of mixing and requires treatment coverage of almost 80% if rates of testing and treatment uptake by all population subgroups are equal. In this case, for fully assortative mixing and 80% coverage endemic prevalence is reduced by 57%. In the presence of heterogeneity in ART uptake, elimination is easier to achieve when the subpopulation with highest risk behavior is tested and treated more often than the rest of the population, and vice versa when it is less. The developed framework can be used to extract information on behavioral heterogeneity from existing data which is otherwise hard to determine from population surveys.

HIV is endemic in populations of MSM in Western countries. As ART reduces transmission risk, increased testing and treatment rates are expected to lower HIV incidence. However, concerns are that in MSM populations changing risk behavior may counteract the impact of ART on transmission. Using a mathematical model, we investigated how heterogeneity in sexual behavior influences the possible effects of a test-and-treat strategy on HIV prevalence and in particular the prospects of eliminating HIV from these populations. We demonstrated that behavioral heterogeneity plays an important role in determining the impact of ART on reducing HIV transmission. Knowledge of behavioral heterogeneity is key in setting intervention goals in populations of MSM.

Estimating HIV Incidence, Time to Diagnosis, and the Undiagnosed HIV Epidemic Using Routine Surveillance Data

BACKGROUND

Estimates of the size of the undiagnosed HIV-infected population are important to understand the HIV epidemic and to plan interventions, including "test-and-treat" strategies.

METHODS

We developed a multi-state back-calculation model to estimate HIV incidence, time between infection and diagnosis, and the undiagnosed population by CD4 count strata, using surveillance data on new HIV and AIDS diagnoses. The HIV incidence curve was modelled using cubic splines. The model was tested on simulated data and applied to surveillance data on men who have sex with men in The Netherlands.

RESULTS

The number of HIV infections could be estimated accurately using simulated data, with most values within the 95% confidence intervals of model predictions. When applying the model to Dutch surveillance data, 15,400 (95% confidence interval [CI] = 15,000, 16,000) men who have sex with men were estimated to have been infected between 1980 and 2011. HIV incidence showed a bimodal distribution, with peaks around 1985 and 2005 and a decline in recent years. Mean time to diagnosis was 6.1 (95% CI = 5.8, 6.4) years between 1984 and 1995 and decreased to 2.6 (2.3, 3.0) years in 2011. By the end of 2011, 11,500 (11,000, 12,000) men who have sex with men in The Netherlands were estimated to be living with HIV, of whom 1,750 (1,450, 2,200) were still undiagnosed. Of the undiagnosed men who have sex with men, 29% (22, 37) were infected for less than 1 year, and 16% (13, 20) for more than 5 years.

CONCLUSIONS

This multi-state back-calculation model will be useful to estimate HIV incidence, time to diagnosis, and the undiagnosed HIV epidemic based on routine surveillance data.

Dispersion of the HIV-1 Epidemic in Men Who Have Sex with Men in the Netherlands: A Combined Mathematical Model and Phylogenetic Analysis

BACKGROUND

The HIV-1 subtype B epidemic amongst men who have sex with men (MSM) is resurgent in many countries despite the widespread use of effective combination antiretroviral therapy (cART). In this combined mathematical and phylogenetic study of observational data, we aimed to find out the extent to which the resurgent epidemic is the result of newly introduced strains or of growth of already circulating strains.

METHODS AND FINDINGS

As of November 2011, the ATHENA observational HIV cohort of all patients in care in the Netherlands since 1996 included HIV-1 subtype B polymerase sequences from 5,852 patients. Patients who were diagnosed between 1981 and 1995 were included in the cohort if they were still alive in 1996. The ten most similar sequences to each ATHENA sequence were selected from the Los Alamos HIV Sequence Database, and a phylogenetic tree was created of a total of 8,320 sequences. Large transmission clusters that included ≥10 ATHENA sequences were selected, with a local support value ≥ 0.9 and median pairwise patristic distance below the fifth percentile of distances in the whole tree. Time-varying reproduction numbers of the large MSM-majority clusters were estimated through mathematical modeling. We identified 106 large transmission clusters, including 3,061 (52%) ATHENA and 652 Los Alamos sequences. Half of the HIV sequences from MSM registered in the cohort in the Netherlands (2,128 of 4,288) were included in 91 large MSM-majority clusters. Strikingly, at least 54 (59%) of these 91 MSM-majority clusters were already circulating before 1996, when cART was introduced, and have persisted to the present. Overall, 1,226 (35%) of the 3,460 diagnoses among MSM since 1996 were found in these 54 long-standing clusters. The reproduction numbers of all large MSM-majority clusters were around the epidemic threshold value of one over the whole study period. A tendency towards higher numbers was visible in recent years, especially in the more recently introduced clusters. The mean age of MSM at diagnosis increased by 0.45 years/year within clusters, but new clusters appeared with lower mean age. Major strengths of this study are the high proportion of HIV-positive MSM with a sequence in this study and the combined application of phylogenetic and modeling approaches. Main limitations are the assumption that the sampled population is representative of the overall HIV-positive population and the assumption that the diagnosis interval distribution is similar between clusters.

CONCLUSIONS

The resurgent HIV epidemic amongst MSM in the Netherlands is driven by several large, persistent, self-sustaining, and, in many cases, growing sub-epidemics shifting towards new generations of MSM. Many of the sub-epidemics have been present since the early epidemic, to which new sub-epidemics are being added.

Potential impact on HIV incidence of higher HIV testing rates and earlier antiretroviral therapy initiation in MSM

BACKGROUND

Increased rates of testing, with early antiretroviral therapy (ART) initiation, represent a key potential HIV-prevention approach. Currently, in MSM in the United Kingdom, it is estimated that 36% are diagnosed by 1 year from infection, and the ART initiation threshold is at CD4 cell count 350/μl. We investigated what would be required to reduce HIV incidence in MSM to below 1 per 1000 person-years (i.e. <535 new infections per year) by 2030, and whether this is likely to be cost-effective.

METHODS

A dynamic, individual-based simulation model was calibrated to multiple data sources on HIV in MSM in the United Kingdom. Outcomes were projected according to future alternative HIV testing and ART initiation scenarios to 2030, considering also potential changes in levels of condomless sex.

RESULTS

For ART use to result in an incidence of close to 1/1000 person-years requires the proportion of all HIV-positive MSM with viral suppression to increase from below 60% currently to 90%, assuming no rise in levels of condomless sex. Substantial increases in HIV testing, such that over 90% of men are diagnosed within a year of infection, would increase the proportion of HIV-positive men with viral suppression to 80%, and it would be 90%, if ART is initiated at diagnosis. The scenarios required for such a policy to be cost-effective are presented.

CONCLUSION

This analysis provides targets for the proportion of all HIV-positive MSM with viral suppression required to achieve substantial reductions in HIV incidence.

Role of oral pre-exposure prophylaxis (PrEP) in current and future HIV prevention strategies

Treatment as prevention is expected to have a major role in reducing HIV incidence, but other prevention interventions will also be required to bring the epidemic under control, particularly among key populations. One or more forms of pre-exposure prophylaxis (PrEP) will likely play a critical role. Oral PrEP with emtricitabine-tenofovir (Truvada®) is currently available in the US and some other countries, but uptake has been slow. We review the concerns that have contributed to this slow uptake and discuss current and future research in this critical area of HIV prevention research.

HIV treatment as prevention: contradictory perspectives from dynamic mathematical models

The preventative effects of antiretroviral therapy for people with HIV have been debated since they were first raised. Models commenced studying the preventive effects of treatment in the 1990s, prior to initial public reports. However, the outcomes of the preventive effects of antiretroviral use were not consistent. Some outcomes of dynamic models were based on unfeasible assumptions, such as no consideration of drug resistance, behavior disinhibition, or economic inputs in poor countries, and unrealistic input variables, for example, overstated initiation time, adherence, coverage, and efficacy of treatment. This paper reviewed dynamic mathematical models to ascertain the complex effects of ART on HIV transmission. This review discusses more conservative inputs and outcomes relative to antiretroviral use in HIV infections in dynamic mathematical models. ART alone cannot eliminate HIV transmission.

Can we rely on the antiretroviral treatment as the only means for human immunodeficiency virusprevention? A Public Health perspective

The evidence that supports the preventive effect of combination antiretroviral treatment (cART) in HIV sexual transmission suggested the so-called 'treatment as prevention' (TAP) strategy as a promising tool for slowing down HIV transmission. As the messages and attitudes towards condom use in the context of TAP appear to be somehow confusing, the aim here is to assess whether relying on cART alone to prevent HIV transmission can currently be recommended from the Public Health perspective. A review is made of the literature on the effects of TAP strategy on HIV transmission and the epidemiology of other sexual transmitted infections (STIs) in the cART era, and recommendations from Public Health institutions on the TAP as of February 2014. The evolution of HIV and other STIs in Barcelona from 2007 to 2012 has also been analysed. Given that the widespread use of cART has coincided with an increasing incidence of HIV and other STIs, mainly amongst men who have sex with men, a combination and diversified prevention methods should always be considered and recommended in counselling. An informed decision on whether to stop using condoms should only be made by partners within stable couples, and after receiving all the up-to-date information regarding TAP. From the public health perspective, primary prevention should be a priority; therefore relying on cART alone is not a sufficient strategy to prevent new HIV and other STIs.

Why the proportion of transmission during early-stage HIV infection does not predict the long-term impact of treatment on HIV incidence

Antiretroviral therapy (ART) reduces the infectiousness of HIV-infected persons, but only after testing, linkage to care, and successful viral suppression. Thus, a large proportion of HIV transmission during a period of high infectiousness in the first few months after infection ("early transmission") is perceived as a threat to the impact of HIV "treatment-as-prevention" strategies. We created a mathematical model of a heterosexual HIV epidemic to investigate how the proportion of early transmission affects the impact of ART on reducing HIV incidence. The model includes stages of HIV infection, flexible sexual mixing, and changes in risk behavior over the epidemic. The model was calibrated to HIV prevalence data from South Africa using a Bayesian framework. Immediately after ART was introduced, more early transmission was associated with a smaller reduction in HIV incidence rate--consistent with the concern that a large amount of early transmission reduces the impact of treatment on incidence. However, the proportion of early transmission was not strongly related to the long-term reduction in incidence. This was because more early transmission resulted in a shorter generation time, in which case lower values for the basic reproductive number (R0) are consistent with observed epidemic growth, and R0 was negatively correlated with long-term intervention impact. The fraction of early transmission depends on biological factors, behavioral patterns, and epidemic stage and alone does not predict long-term intervention impacts. However, early transmission may be an important determinant in the outcome of short-term trials and evaluation of programs.

Modelling in concentrated epidemics: informing epidemic trajectories and assessing prevention approaches

PURPOSE OF THE REVIEW

This review summarizes recent mathematical modelling studies conducted among key populations including MSM, people who inject drugs (PWID), and female sex workers (FSWs) in low prevalence settings used as a marker of concentrated epidemics.

RECENT FINDINGS

Most recent studies focused on MSM, Asian settings or high-income countries, studied the transmission dynamics or modelled pre-exposure prophylaxis, treatment as prevention or behavioural interventions specific to each key population (e.g., needle exchange programme or use of low-dead space syringes for PWID). Biological interventions were deemed effective and cost-effective, though still expensive, and often deemed unlikely to result in HIV elimination if used alone. Targeting high-risk individuals even within key populations improved efficiency. Some studies made innovative use of models to formally evaluate HIV prevention programmes, to interpret genetic or co-infection data, and to address methodological questions and validate epidemiological tools.

CONCLUSION

More work is needed to optimize combination prevention focusing on key populations in different settings. The gaps identified include the limited number of studies modelling drug resistance, structural interventions, treatment as prevention among FSWs, and estimating the contribution of key populations to overall transmission in different settings.

Access to post-exposure prophylaxis following sexual exposure for men who have sex with men in an Irish healthcare setting

Men who have sex with men experience disproportionate rates of HIV acquisition. Post-exposure prophylaxis following unprotected sexual exposure reduces HIV transmission. Our aim was to assess access to post-exposure prophylaxis for men who have sex with men in Irish emergency departments. We contacted all national 24-hour adult emergency departments describing two scenarios; a seronegative man who has sex with men receiving unprotected insertive anal intercourse from a seropositive partner and secondly a woman sustaining a needle-stick injury from an unknown source. We recorded and compared responses regarding post-exposure prophylaxis advice in each situation. High proportions of emergency departments offered post-exposure prophylaxis for both situations despite minimal evidence to support use in needle-stick injury. Men who have sex with men were less likely to be asked to attend emergency departments for post-exposure prophylaxis administration than a person experiencing needle-stick injury. Men who have sex with men were less likely to be offered baseline serological testing for blood borne infections. Men who have sex with men were as likely as needle-stick injury to receive advice from healthcare workers in emergency departments and consultation durations were similar. This study identifies a need to educate healthcare workers in emergency departments on appropriate use of post-exposure prophylaxis following sexual exposure for men who have sex with men. Health care workers must appreciate the importance of post-exposure prophylaxis presentations as opportunities for intervention and HIV screening.

Prevalence of unprotected anal intercourse among men who have sex with men in China: an updated meta-analysis

OBJECTIVE

The purpose of this review was to assess the prevalence of unprotected anal intercourse (UAI) among men who have sex with men (MSM) in China.

METHODS

A comprehensive search was conducted including online databases like "Wanfang", Chinese National Knowledge Infrastructure, PubMed and manual searches. Analyses using random-effects models were performed to estimate the prevalence of UAI among MSM in China.

RESULTS

Sixty-two articles reporting eighty-two studies were selected. The pooled prevalence rates of UAI with any male partner, with regular male partners, with non-regular male partners, with casual male partners, and with commercial male partners among MSM were 53%(95%CI: 51-56%), 45%(95%CI: 39-51%), 34%(95%CI: 24-45%), 33%(95%CI: 30-36%), 12% (95%CI: 5-26%), respectively. A cumulative meta-analysis found that the pooled UAI prevalence decreased over time.

CONCLUSIONS

Although the prevalence of UAI with male partners among MSM in China presents a decreasing trend over the past decade, the concomitant rise in HIV prevalence and incidence indicates that current prevention intervention efforts are insufficient to effectively contain the spread of HIV. Therefore, the persistently high prevalence of risky sexual behaviors underscores the need for innovative and effective prevention strategies among MSM.

Antiretrovirals for HIV prevention: when should they be recommended?

Since the introduction of the first antiretroviral agent for HIV treatment, information on antiretroviral therapy (ART) effectiveness has grown continuously. In recent years, there has also been a growth of interest in use of ART for the prevention of HIV transmission, either by reducing the infectivity of the infected person or by protecting the uninfected individuals from HIV acquisition. The purpose of this review is to summarize the body of evidence available for treatment as prevention and pre-exposure prophylaxis and their effectiveness in prevention of infection. In addition, our aim is to discuss the operational aspects of both prevention strategies and to provide commentary for future HIV prevention programs.

Toward an endgame: finding and engaging people unaware of their HIV-1 infection in treatment and prevention

Epidemic modeling suggests that a major scale-up in HIV treatment could have a dramatic impact on HIV incidence. This has led both researchers and policymakers to set a goal of an "AIDS-Free Generation." One of the greatest obstacles to achieving this objective is the number of people with undiagnosed HIV infection. Despite recent innovations, new research strategies are needed to identify, engage, and successfully treat people who are unaware of their infection.

Can treatment-based HIV prevention curb the epidemic among gay and other men who have sex with men? A narrative synthesis of increasing evidence for moderating and countervailing effects

As HIV epidemics among gay and other men who have sex with men (GMSM) persist worldwide, the importance of novel prevention approaches is recognised. Evidence that antiretroviral therapy (ART) can decrease the likelihood of infection is informing emerging HIV prevention approaches, encompassing early initiation of treatment as prevention by people living with HIV and use of antiretroviral drugs as pre-exposure prophylaxis for people presumed to be uninfected. Despite widespread excitement, robust evidence of the beneficial effects of ART-based HIV prevention for GMSM remains limited. Also, theoretical models project widely varying effects of ART-based prevention on the future course of HIV epidemics among GMSM, drawing attention to the possible moderating role of differences in the achievements of local HIV responses and the critical importance of sustained protective sexual practices into the future. Ecological analyses and simulations of ongoing epidemics in major gay communities illustrate that the preventive effects of ART in many settings are being offset by increased sexual risk-taking, as reflected in stable or increasing HIV infection rates. Also, the effects of scaling up HIV testing and treatment among GMSM in settings that are often considered prime examples of the success of ART-based prevention may be levelling as ‘scope for improvement’ diminishes. ART-based approaches further extend the HIV prevention toolkit and substantially increase people’s options to protect themselves and others. The future impact of ART-based prevention on HIV epidemics among GMSM ultimately depends on whether heralded responses offset, attenuate or compound the ongoing social and behavioural changes that drive increased sexual risk.

Health benefits, costs, and cost-effectiveness of earlier eligibility for adult antiretroviral therapy and expanded treatment coverage: a combined analysis of 12 mathematical models

BACKGROUND

New WHO guidelines recommend ART initiation for HIV-positive persons with CD4 cell counts ≤500 cells/µL, a higher threshold than was previously recommended. Country decision makers must consider whether to further expand ART eligibility accordingly.

METHODS

We used multiple independent mathematical models in four settings-South Africa, Zambia, India, and Vietnam-to evaluate the potential health impact, costs, and cost-effectiveness of different adult ART eligibility criteria under scenarios of current and expanded treatment coverage, with results projected over 20 years. Analyses considered extending eligibility to include individuals with CD4 ≤500 cells/µL or all HIV-positive adults, compared to the previous recommendation of initiation with CD4 ≤350 cells/µL. We assessed costs from a health system perspective, and calculated the incremental cost per DALY averted ($/DALY) to compare competing strategies. Strategies were considered 'very cost-effective' if the $/DALY was less than the country's per capita gross domestic product (GDP; South Africa: $8040, Zambia: $1425, India: $1489, Vietnam: $1407) and 'cost-effective' if $/DALY was less than three times per capita GDP.

FINDINGS

In South Africa, the cost per DALY averted of extending ART eligibility to CD4 ≤500 cells/µL ranged from $237 to $1691/DALY compared to 2010 guidelines; in Zambia, expanded eligibility ranged from improving health outcomes while reducing costs (i.e. dominating current guidelines) to $749/DALY. Results were similar in scenarios with substantially expanded treatment access and for expanding eligibility to all HIV-positive adults. Expanding treatment coverage in the general population was therefore found to be cost-effective. In India, eligibility for all HIV-positive persons ranged from $131 to $241/DALY and in Vietnam eligibility for CD4 ≤500 cells/µL cost $290/DALY. In concentrated epidemics, expanded access among key populations was also cost-effective.

INTERPRETATION

Earlier ART eligibility is estimated to be very cost-effective in low- and middle-income settings, although these questions should be revisited as further information becomes available. Scaling-up ART should be considered among other high-priority health interventions competing for health budgets.

FUNDING

The Bill and Melinda Gates Foundation and World Health Organization.

Antiretroviral treatment of HIV-1 prevents transmission of HIV-1: where do we go from here?

Antiretroviral drugs that inhibit viral replication were expected to reduce transmission of HIV by lowering the concentration of HIV in the genital tract. In 11 of 13 observational studies, antiretroviral therapy (ART) provided to an HIV-infected index case led to greatly reduced transmission of HIV to a sexual partner. In the HPTN 052 randomised controlled trial, ART used in combination with condoms and counselling reduced HIV transmission by 96·4%. Evidence is growing that wider, earlier initiation of ART could reduce population-level incidence of HIV. However, the full benefits of this strategy will probably need universal access to very early ART and excellent adherence to treatment. Challenges to this approach are substantial. First, not all HIV-infected individuals can be located, especially people with acute and early infection who are most contagious. Second, the ability of ART to prevent HIV transmission in men who have sex with men (MSM) and people who use intravenous drugs has not been shown. Indeed, the stable or increased incidence of HIV in MSM in some communities where widespread use of ART has been established emphasises the concern that not enough is known about treatment as prevention for this crucial population. Third, although US guidelines call for immediate use of ART, such guidelines have not been embraced worldwide. Some experts do not believe that immediate or early ART is justified by present evidence, or that health-care infrastructure for this approach is sufficient. These concerns are very difficult to resolve. Ongoing community-based prospective trials of early ART are likely to help to establish the population-level benefit of ART, and-if successful-to galvanise treatment as prevention.