The impact of pre-exposure prophylaxis (PrEP) on HIV epidemics in Africa and India: a simulation study

Perspectives of female sex workers on HIV pre-exposure prophylaxis delivery in Uganda: A qualitative study

Background

HIV pre-exposure prophylaxis (PrEP) is underutilized by cisgender female sex workers (FSW) despite its proven effectiveness. This study aimed to understand the experiences of FSW with PrEP services in Uganda to inform HIV programming for this key population.

Methods

We conducted qualitative interviews with 19 FSW between June and July 2022 at the Most at Risk Populations Initiative clinic, Mulago Hospital, Kampala, to explore experiences with accessing PrEP Indepth interviews explored: (1) descriptions of where and how PrEP was obtained; (2) perspectives on current approaches for accessing PrEP; and (3) individual encounters with PrEP services. Data were analyzed through inductive thematic analysis.

Results

Three key themes emerged for FSW perspectives on PrEP service delivery. FSW highlighted the positive impact of a welcoming clinic environment, which motivated FSW to initiate PrEP and fostered a sense of connectedness within their community. They also reported feeling accepted, secure, and free from prejudice when accessing PrEP through facility-based services. The second explores the obstacles faced by FSW, such as lengthy wait times at clinics, inadequate provider support, and lack of sensitivity training which hindered their access to PrEP The third sheds light on how HIV-related stigma negatively impacted the delivery of community-based PrEP for FSW. While community-based distribution offered convenience and helped mitigate stigma, clinic-based care provided greater anonymity and was perceived as offering higher-quality care. Overall, FSWs emphasized the critical role of friendly healthcare providers, social support, and non-stigmatizing environments in promoting successful utilization of PrEP.

Conclusion

The study findings offer insights that can support HIV programs in optimizing PrEP delivery for FSW. Establishing easily accessible drug pick-up locations, prioritizing privacy, addressing and improving health workers' attitudes, and providing regular reminders could enhance PrEP access for FSW and decrease HIV acquisition.

Identifying Individuals at High Risk for HIV and Sexually Transmitted Infections With an Artificial Intelligence-Based Risk Assessment Tool

Background

We have previously developed an artificial intelligence-based risk assessment tool to identify the individual risk of HIV and sexually transmitted infections (STIs) in a sexual health clinical setting. Based on this tool, this study aims to determine the optimal risk score thresholds to identify individuals at high risk for HIV/STIs.

Methods

Using 2008-2022 data from 216 252 HIV, 227 995 syphilis, 262 599 gonorrhea, and 320 355 chlamydia consultations at a sexual health center, we applied MySTIRisk machine learning models to estimate infection risk scores. Optimal cutoffs for determining high-risk individuals were determined using Youden's index.

Results

The HIV risk score cutoff for high risk was 0.56, with 86.0% sensitivity (95% CI, 82.9%-88.7%) and 65.6% specificity (95% CI, 65.4%-65.8%). Thirty-five percent of participants were classified as high risk, which accounted for 86% of HIV cases. The corresponding cutoffs were 0.49 for syphilis (sensitivity, 77.6%; 95% CI, 76.2%-78.9%; specificity, 78.1%; 95% CI, 77.9%-78.3%), 0.52 for gonorrhea (sensitivity, 78.3%; 95% CI, 77.6%-78.9%; specificity, 71.9%; 95% CI, 71.7%-72.0%), and 0.47 for chlamydia (sensitivity, 68.8%; 95% CI, 68.3%-69.4%; specificity, 63.7%; 95% CI, 63.5%-63.8%). High-risk groups identified using these thresholds accounted for 78% of syphilis, 78% of gonorrhea, and 69% of chlamydia cases. The odds of positivity were significantly higher in the high-risk group than otherwise across all infections: 11.4 (95% CI, 9.3-14.8) times for HIV, 12.3 (95% CI, 11.4-13.3) for syphilis, 9.2 (95% CI, 8.8-9.6) for gonorrhea, and 3.9 (95% CI, 3.8-4.0) for chlamydia.

Conclusions

Risk scores generated by the AI-based risk assessment tool MySTIRisk, together with Youden's index, are effective in determining high-risk subgroups for HIV/STIs. The thresholds can aid targeted HIV/STI screening and prevention.

Understanding issues around use of oral pre exposure prophylaxis among female sex workers in India

BACKGROUND

Empowering female sex workers (FSWs) through women controlled HIV prevention option has been in focus globally. FSWs are important target for oral pre exposure prophylaxis (PrEP). A multi-centric qualitative study was conducted to explore the FSWs' willingness to use oral PrEP in India.

METHODS

Seventy three interviews and 02 focus group discussions were conducted at 3 high HIV prevalent states in India during 2013-14. Study explored issues around willingness to use oral PrEP. The study was approved by the respective institutional ethics committee of the study sites. Thematic analysis using grounded theory approach was used to analyze the data in N-VIVO version 8.0.

RESULTS

Thematic analysis showed events of forced condom-less sex. FSWs believed that oral PrEP could provide independence, financial gains, and privacy and therefore hoped to use it as an alternative to male condom. However, any impact on physical/ aesthetic attributes and reproductive system were not acceptable and could become a barrier. Provider initiated oral PrEP was not preferred. Providers voiced safety monitoring concerns. Adherence emerged as a challenge because of: (1) alcohol use; (2) taking PrEP tablet each day being boring; (3) Stigma because Oral PrEP is ARV based. Alcohol use and dread of repetitive dose brings forth the need for long acting oral PrEP.

CONCLUSION

Oral PrEP is acceptable among FSWs; it should be rolled out alongside strong messages on STI protection and PrEP as compliment to condoms. PrEP roll out requires educating communities about HIV treatment versus prevention. Long-acting oral PrEP could address both 'boredom' and alcoholism and sustain adherence.

Mathematical Model Impact Analysis of a Real-Life Pre-exposure Prophylaxis and Treatment-As-Prevention Study Among Female Sex Workers in Cotonou, Benin

BACKGROUND

Daily pre-exposure prophylaxis (PrEP) and treatment-as-prevention (TasP) reduce HIV acquisition and transmission risk, respectively. A demonstration study (2015-2017) assessed TasP and PrEP feasibility among female sex workers (FSW) in Cotonou, Benin.

SETTING

Cotonou, Benin.

METHODS

We developed a compartmental HIV transmission model featuring PrEP and antiretroviral therapy (ART) among the high-risk (FSW and clients) and low-risk populations, calibrated to historical epidemiological and demonstration study data, reflecting observed lower PrEP uptake, adherence and retention compared with TasP. We estimated the population-level impact of the 2-year study and several 20-year intervention scenarios, varying coverage and adherence independently and together. We report the percentage [median, 2.5th-97.5th percentile uncertainty interval (95% UI)] of HIV infections prevented comparing the intervention and counterfactual (2017 coverages: 0% PrEP and 49% ART) scenarios.

RESULTS

The 2-year study (2017 coverages: 9% PrEP and 83% ART) prevented an estimated 8% (95% UI 6-12) and 6% (3-10) infections among FSW over 2 and 20 years, respectively, compared with 7% (3-11) and 5% (2-9) overall. The PrEP and TasP arms prevented 0.4% (0.2-0.8) and 4.6% (2.2-8.7) infections overall over 20 years, respectively. Twenty-year PrEP and TasP scale-ups (2035 coverages: 47% PrEP and 88% ART) prevented 21% (17-26) and 17% (10-27) infections among FSW, respectively, and 5% (3-10) and 17% (10-27) overall. Compared with TasP scale-up alone, PrEP and TasP combined scale-up prevented 1.9× and 1.2× more infections among FSW and overall, respectively.

CONCLUSIONS

The demonstration study impact was modest, and mostly from TasP. Increasing PrEP adherence and coverage improves impact substantially among FSW, but little overall. We recommend TasP in prevention packages.

Introducing pre-exposure prophylaxis to prevent HIV acquisition among men who have sex with men in Sweden: insights from a mathematical pair formation model

OBJECTIVES

Since 2017, the Public Health Agency of Sweden recommends that pre-exposure prophylaxis (PrEP) for HIV should be offered to high-risk individuals, in particular to men who have sex with men (MSM). The objective of this study is to develop a mathematical model investigating the effect of introducing PrEP to MSM in Sweden.

DESIGN

A pair formation model, including steady and casual sex partners, is developed to study the impact of introducing PrEP. Two groups are included in the model: sexually high active MSM and sexually low active MSM. Three mixing assumptions between the groups are considered.

SETTING

A gay-friendly MSM HIV/sexually transmitted infection testing clinic in Stockholm, Sweden. This clinic started offering PrEP to MSM in October 2018.

PARTICIPANTS

The model is calibrated according to detailed sexual behaviour data gathered in 2015 among 403 MSM.

RESULTS

By targeting sexually high active MSM, a PrEP coverage of 3.5% of the MSM population (10% of all high actives) would result in the long-term HIV prevalence to drop considerably (close to 0%). While targeting only low actives would require a PrEP coverage of 35% for a similar reduction. The main effect of PrEP is the reduced susceptibility, whereas the increased HIV testing rate (every third month) among PrEP users plays a lesser role.

CONCLUSIONS

To create a multifaceted picture of the effects of interventions against HIV, we need models that include the different stages of HIV infection and real-world data on detailed sexual behaviour to calibrate the mathematical models. Our findings conclude that targeting HIV high-risk individuals, within HIV risk populations such as MSM, with PrEP programmes could greatly decrease the long-term HIV prevalence in Sweden. Therefore, risk stratification of individuals is of importance in PrEP implementation programmes, to ensure optimising the effect and cost-effectiveness of such programmes.

Modeling HIV Pre-Exposure Prophylaxis

Pre-exposure prophylaxis (PrEP) has emerged as a promising strategy for preventing the transmission of HIV. Although only one formulation is currently approved for PrEP, research into both new compounds and new delivery systems for PrEP regimens offer intriguing challenges from the perspective of pharmacokinetic and pharmacodynamic modeling. This review aims to provide an overview the current modeling landscape for HIV PrEP, focused on PK/PD and QSP models relating to antiretroviral agents. Both current PrEP treatments and new compounds that show promise as PrEP agents are highlighted, as well as models of uncommon administration routes, predictions based on models of mechanism of action and viral dynamics, and issues related to adherence to therapy. The spread of human immunodeficiency virus (HIV) remains one of the foremost global health concerns. In the absence of a vaccine, other prophylactic strategies have been developed to prevent HIV transmission. One approach, known as pre-exposure prophylaxis (PrEP), allows HIV-negative individuals who are at high risk of exposure to the virus, be it through an HIV-positive sexual partner or through the shared use of drug injection equipment, to substantially reduce the risk of developing an HIV infection. PrEP is a relatively recent approach to combating the HIV epidemic, with the only currently approved treatment being Truvada, a daily oral antiretroviral (ARV) therapy initially indicated in the treatment of active HIV-1 infections, but approved for HIV PrEP in 2012. Although PrEP therapy has consistently demonstrated high efficacy in preventing HIV infection, this efficacy is dependent on patient adherence to the prescribed treatment regimen. This can present a significant problem in low- and middle-income countries, which may lack the infrastructure to provide sufficient access to PrEP medication to maintain daily dosing regimens. Furthermore, while the conventional approach has generally been to advocate for continuous administration akin to regimens used for viral suppression in infected patients, there has been some discussion of whether a better treatment paradigm might be to push for PrEP therapy primarily during those known periods of heightened exposure risk, while relying on post-exposure prophylaxis regimens to prevent infection after unanticipated exposures during low-risk periods. These considerations have led to a push for the development of long-duration and on-demand PrEP formulations, including subdermal and subcutaneous implants, slow-release intramuscular depot injections, vaginal and rectal antimicrobial gels, and intravaginal rings and dissolving films. PrEP therapy is a quickly evolving field, with a variety of antiretroviral compounds and formulations under investigation. This review aims to report on notable drugs and formulations from a pharmacokinetic/pharmacodynamic (PK/PD) modeling perspective. Given the nature of PrEP as a preventive therapy designed for long-term use, clinical trials for PrEP therapies can last for months or even years, particularly in the case of long-duration formulations. Furthermore, in contrast to antiretroviral trials in infected patients, pharmacodynamic endpoints in PrEP therapies are difficult to quantify, as the primary endpoint for efficacy is generally the rate of seroconversion. Computational modeling approaches offer flexible and powerful tools to provide insight into drug behavior in clinical settings, and can ultimately reduce the time, expense, and patient burden incurred in the development of PrEP therapies.

Community perspectives on barriers and challenges to HIV pre-exposure prophylaxis access by men who have sex with men and female sex workers access in Nigeria

Background

Men who have sex with men (MSM), female sex workers (FSW) have critical needs for effective HIV prevention tools. This study identified perspectives of MSM, FSW and policy makers on the needs for, barriers to, and challenges with pre-exposure HIV prophylaxis (PrEP); and the logistics required to support roll-out of PrEP for MSM and FSW in Nigeria.

Methods

Qualitative and quantitative data were collected through a cross-sectional study. The quantitative data were collected through an online survey administered to 519 MSM, FSW and transgender respondents. The qualitative data were collected through 22 focus group discussions with 140 MSM and 80 FSW, and a two-day consultative workshop with 65 participants. Two open-ended questions in the online survey were also a source of qualitative data. Results of the quantitative data were reported descriptively; the qualitative data were inductively examined with a content analytic approach to construct descriptive categories. The findings from the quantitative and qualitative responses were triangulated.

Results

Four hundred and ninety-four (95.2%) online respondents had heard about PrEP through community dialogue (71.3%), and 439 (84.6%) supported its use by MSM and FSW. Fewer than half of the respondents were aware of the clinical care required for PrEP, and misconceptions about PrEP were common. Stated barriers to PrEP uptake were stigma, cost, frequency of HIV counseling and treatment services required, and possible drug-drug interactions. Concerns included possible condom migration, increased risk for sexually transmitted infections and pregnancy for FSW, and poor adherence to medication and hospital schedules. Participants felt that trained peer educators and HIV-test counselors could provide information and refer clients to clinics that provide PrEP. PrEP can be provided through peer-led facilities for MSM and FSW, though its access should be expanded to all persons who are at substantial risk for HIV to prevent negative labeling of PrEP. Public awareness about the use of antiretrovirals for HIV prevention is needed to prevent labeling of PrEP users as being HIV positive.

Conclusion

Although MSM and FSW are interested in the use of PrEP, numerous individual and structural barriers need to be addressed to facilitate access to it in Nigeria.

A modeling framework to inform preexposure prophylaxis initiation and retention scale-up in the context of 'Getting to Zero' initiatives

OBJECTIVE(S)

'Getting to Zero' (GTZ) initiatives aim to eliminate new HIV infections over a projected time frame. Increased preexposure prophylaxis (PrEP) uptake among populations with the highest HIV incidence, such as young Black MSM, is necessary to accomplish this aim. Agent-based network models (ABNMs) can help guide policymakers on strategies to increase PrEP uptake.

DESIGN

Effective PrEP implementation requires a model that incorporates the dynamics of interventions and dynamic feedbacks across multiple levels including virus, host, behavior, networks, and population. ABNMs are a powerful tool to incorporate these processes.

METHODS

An ABNM, designed for and parameterized using data for young Black MSM in Illinois, was used to compare the impact of PrEP initiation and retention interventions on HIV incidence after 10 years, consistent with GTZ timelines. Initiation interventions selected individuals in serodiscordant partnerships, or in critical sexual network positions, and compared with a controlled setting where PrEP initiators were randomly selected. Retention interventions increased the mean duration of PrEP use. A combination intervention modeled concurrent increases in PrEP initiation and retention.

RESULTS

Selecting HIV-negative individuals for PrEP initiation in serodiscordant partnerships resulted in the largest HIV incidence declines, relative to other interventions. For a given PrEP uptake level, distributing effort between increasing PrEP initiation and retention in combination was approximately as effective as increasing only one exclusively.

CONCLUSION

Simulation results indicate that expanded PrEP interventions alone may not accomplish GTZ goals within a decade, and integrated scale-up of PrEP, antiretroviral therapy, and other interventions might be necessary.

HIV control strategies for sex worker-client contact networks

Controlling the spread of HIV among hidden, high-risk populations such as survival sex workers and their clients is becoming increasingly important in the ongoing fight against HIV/AIDS. Several sociological and structural factors render general control strategies ineffective in these settings; instead, focused prevention, testing and treatment strategies which take into account the nature of survival sex work are required. Using a dynamic bipartite network model of sexual contacts, we investigate the optimal distribution of treatment and preventative resources among sex workers and their clients; specifically, we consider control strategies that randomly allocate antiretroviral therapy and pre-exposure prophylaxis within each subpopulation separately. Motivated by historical data from a South African mining community, three main asymmetries between sex workers and clients are considered in our model: relative population sizes, migration rates and partner distributions. We find that preventative interventions targeted at female sex workers are the lowest cost strategies for reducing HIV prevalence, since the sex workers form a smaller population and have, on average, more sexual contacts. However, the high migration rate among survival sex workers limits the extent to which prevalence can be reduced using this strategy. To achieve a further reduction in HIV prevalence, testing and treatment in the client population cannot be ignored.

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.

"We know this will be hard at the beginning, but better in the long term": understanding PrEP uptake in the general population in Eswatini

Information regarding HIV pre-exposure prophylaxis (PrEP) for the general population is largely lacking, because the majority of PrEP demonstration projects have focused on key populations. This qualitative study examines barriers and facilitators to PrEP uptake and adherence among the general population in Eswatini, where PrEP is offered through public-sector primary-care clinics. We analysed 106 semi-structured in-depth interviews with healthcare workers (n = 26), stakeholders (n = 30), and clients who initiated, continued, declined or discontinued PrEP (n = 50). Some healthcare workers and stakeholders feared that PrEP would reduce condom use and cause drug resistance, while some clients feared possible side effects and the reaction of family members when learning of PrEP use. At the same time, respondents across all groups valued that PrEP could be taken without partner knowledge or consent, and that PrEP was available via public sector clinics. Clients felt that PrEP relieved the fear of HIV infection and thus bolstered enjoyment during sex. Overall, respondents described the general population approach to PrEP delivery as enabling and life-improving, despite the above concerns. Respondents recommended to create community PrEP promotion and delivery, gain community leaders' approval and understanding of PrEP, shorten the PrEP initiation process, and target men and adolescent girls.

Gonorrhoea and chlamydia diagnosis as an entry point for HIV pre-exposure prophylaxis: a modelling study

OBJECTIVES

Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) increase the risk of HIV transmission among men who have sex with men (MSM). Diagnosis of NG/CT may provide an efficient entry point for prevention of HIV through the delivery of pre-exposure prophylaxis (PrEP); however, the additional population-level impact of targeting PrEP to MSM diagnosed with NG/CT is unknown.

DESIGN

An agent-based simulation model of NG/CT and HIV cocirculation among MSM calibrated against census data, disease surveillance reports and the US National HIV Behavioral Surveillance study.

SETTING

Baltimore City, Maryland, USA.

INTERVENTIONS

PrEP implementation was modelled under three alternative scenarios: (1) PrEP delivery at NG/CT diagnosis (targeted delivery), (2) PrEP evaluation at NG/CT screening/testing and (3) PrEP evaluation in the general community (untargeted).

MAIN OUTCOME

The projected incidence of HIV after 20 years of PrEP delivery under two alternatives: when equal numbers of MSM are (1) screened for PrEP or (2) receive PrEP in each year.

RESULTS

Assuming 60% uptake and 60% adherence, targeting PrEP to MSM diagnosed with NG/CT could reduce HIV incidence among MSM in Baltimore City by 12.4% (95% uncertainty range (UR) 10.3% to 14.4%) in 20 years, relative to no PrEP. Expanding the coverage of NG/CT screening (such that individuals experience a 50% annual probability of NG/CT screening and evaluation for PrEP on NG/CT diagnosis) can further increase the impact of targeted PrEP to generate a 22.0% (95% UR 20.1% to 23.9%) reduction in HIV incidence within 20 years. When compared with alternative implementation scenarios, PrEP evaluation at NG/CT diagnosis increased impact of PrEP on HIV incidence by 1.5(95% UR 1.1 to 1.9) times relative to a scenario in which PrEP evaluation happened at the time of NG/CT screening/testing and by 1.6 (95% UR 1.2 to 2.2) times relative to evaluating random MSM from the community.

CONCLUSIONS

Targeting MSM infected with NG/CT increases the efficiency and effectiveness of PrEP delivery. If high levels of sexually transmitted infection screening can be achieved at the community level, NG/CT diagnosis may be a highly effective entry point for PrEP initialisation.

Pre-exposure Prophylaxis Among Men Who have Sex with Men: Dual Motivational Model of Intention to Use Pre-exposure Prophylaxis

Men who have sex with men (MSM) account for most new HIV infections in the United States. Despite representing a fraction of the population, MSM make up an estimated 65% of new infections. To address this epidemic, pre-exposure prophylaxis (PrEP) is recommended to supplement condom use. Despite its effectiveness, PrEP uptake among MSM is low. Few studies have employed theoretical approaches to understand PrEP use intention. Incorporating factors like safe sex fatigue, expectation of better sexual experiences, and perceived risk are proposed in this dual motivational path model of PrEP use intention. This model hypothesized that PrEP use intention is influenced by two key pathways: (1) protection motivation pathway, and (2) sexual expectancy pathway. Data were collected using social networking applications from 402 MSM. The model was tested using structural equation modeling. We elaborate the complex decision-making process proposed by this novel theoretical model and discuss its practical implications.

"The Time Has Arrived": Perceptions of Behavioral Adjustments in the Context of Pre-Exposure Prophylaxis Availability Among Adolescents in South Africa

Antiretroviral pre-exposure prophylaxis (PrEP) holds enormous potential to reduce HIV acquisition in key populations globally. We conducted an exploratory PrEP acceptability study using qualitative methodology among adolescents and service providers in the Western Cape Province of South Africa to inform future PrEP implementation challenges in South Africa and other high-prevalence African countries. Semistructured focus groups and in-depth individual interviews were conducted among 57 adolescents 16-17 years of age, living with and without HIV, and 25 clinical service providers. Adolescents and service providers expressed concerns that the availability of PrEP would lead to sexual disinhibition and a reduction in condom use among adolescents. Unexpected positive impacts included predictions that PrEP might encourage disclosure in serodiscordant partnerships and help normalize pill-taking in the community. Careful age, gender, and developmentally appropriate messaging will be needed to ensure adolescents understand partial efficacy and view PrEP as a component of combination prevention.

Pre-exposure prophylaxis: awareness, acceptability and risk compensation behaviour among men who have sex with men and the transgender population

OBJECTIVES

This exploratory study examined the facilitators of and barriers to acceptance of pre-exposure prophylaxis (PrEP) and potential risk compensation behaviour emerging from its use among men who have sex with men (MSM) and transgender individuals (TGs) in India.

METHODS

A questionnaire was administered to 400 individuals registered with a targeted intervention programme. Logistic regression models were used to identify facilitators of and barriers to PrEP acceptance.

RESULTS

The respondents consisted of 68% MSM and 32% TGs. Risk behaviour categorization identified 40% as low risk, 41% as medium risk and, 19% as high risk for HIV infection. About 93% of the respondents were unaware of PrEP, but once informed about it, 99% were willing to use PrEP. The facilitators of PrEP acceptance were some schooling [odds ratio (OR) 2.16; P = 0.51], being married or in a live-in relationship (OR 2.08; P = 0.46), having a high calculated risk (OR 3.12; P = 0.33), and having a high self-perceived risk (OR 1.8; P = 0.35). Increasing age (OR 2.12; P = 0.04) was a significant barrier. TGs had higher odds of acceptance of PrEP under conditions of additional cost (OR 2.12; P = 0.02) and once-daily pill (OR 2.85; P = 0.04). Individuals identified as low risk for HIV infection showed lower odds of potential risk compensation, defined as more sexual partners (OR 0.8; P = 0.35), unsafe sex with new partners (OR 0.71; P = 0.16), and decreased condom use with regular partners (OR 0.95; P = 0.84), as compared with medium-risk individuals. The associations, although not statistically significant, are nevertheless important for public health action given the limited scientific evidence on PrEP use among MSM and TGs in India.

CONCLUSIONS

With high acceptability and a low likelihood of risk compensation behaviour, PrEP can be considered as an effective prevention strategy for HIV infection among MSM and TGs in India.

The Impact of Preexposure Prophylaxis Among Men Who Have Sex With Men: An Individual-Based Model

OBJECTIVES

Preexposure prophylaxis (PrEP) is recommended for preventing HIV infection among individuals at high risk, including men who have sex with men (MSM). Although its individual-level efficacy is proven, questions remain regarding population-level impact of PrEP implementation.

DESIGN

We developed an agent-based simulation of HIV transmission among MSM, accounting for demographics, sexual contact network, HIV disease stage, and use of antiretroviral therapy. We use this framework to compare PrEP delivery strategies in terms of impact on HIV incidence and prevalence.

RESULTS

The projected reduction in HIV incidence achievable with PrEP reflects both population-level coverage and individual-level adherence (as a proportion of days protected against HIV transmission). For example, provision of PrEP to 40% of HIV-negative MSM reporting more than one sexual partner in the last 12 months, taken with sufficient adherence to provide protection on 40% of days, can reduce HIV incidence by 9.5% (95% uncertainty range: 8%-11%) within 5 years. However, if this could be increased to 80% coverage on 80% of days (eg, through mass campaigns with a long-acting injectable formulation), a 43% (42%-44%) reduction in HIV incidence could be achieved. Delivering PrEP to MSM at high risk for HIV acquisition can augment population-level impact up to 1.8-fold.

CONCLUSIONS

If highly ambitious targets for coverage and adherence can be achieved, PrEP can substantially reduce HIV incidence in the short-term. Although the reduction in HIV incidence largely reflects the proportion of person-years protected, the efficiency of PrEP delivery can be enhanced by targeting high-risk populations.

Healthcare Access and PrEP Continuation in San Francisco and Miami After the US PrEP Demo Project

BACKGROUND

Pre-exposure prophylaxis (PrEP) for prevention of HIV infection has demonstrated efficacy in randomized controlled trials and in demonstration projects. For PrEP implementation to result in significant reductions in HIV incidence for men who have sex with men in the United States, sufficient access to PrEP care and continued engagement outside of demonstration projects is required.

METHODS

We report the results of a follow-up survey of 173 former participants from the Miami and San Francisco sites of the US PrEP Demo Project, administered 4-6 months after study completion.

RESULTS

Survey respondents continued to frequently access medical care and had a high incidence of sexually transmitted infections after completion of the Demo Project, indicating ongoing sexual risk behavior. Interest in continuing PrEP was high with 70.8% indicating that they were "very interested" in continuing PrEP. Among respondents, 39.9% reported continuation of PrEP after completion of the Demo Project, largely through their primary care providers and frequently at low or no cost. Variability in access and engagement was seen, with participants from the San Francisco site, those with medical insurance, and those with a primary care provider at the end of the Demo Project more likely to successfully obtain PrEP medication. Two respondents reported HIV seroconversion in the period between study completion and the follow-up survey.

CONCLUSIONS

Additional effort to increase equitable access to PrEP outside of demonstration projects is needed to realize the potential impact of this evidence-based prevention intervention.

Awareness and Acceptability of Pre-exposure HIV Prophylaxis Among Men Who have Sex with Men in Baltimore

This paper assessed characteristics associated with awareness of and willingness to take pre-exposure prophylaxis (PrEP) among Baltimore men who have sex with men (MSM). We used data from BESURE-MSM3, a venue-based cross-sectional HIV surveillance study conducted among MSM in 2011. Multivariate regression was used to identify characteristics associated with PrEP knowledge and acceptability among 399 participants. Eleven percent had heard of PrEP, 48% would be willing to use PrEP, and none had previously used it. In multivariable analysis, black race and perceived discrimination against those with HIV were significantly associated with decreased awareness, and those who perceived higher HIV discrimination reported higher acceptability of PrEP. Our findings indicate a need for further education about the potential utility of PrEP in addition to other prevention methods among MSM. HIV prevention efforts should address the link between discrimination and potential PrEP use, especially among men of color.

Pre-exposure prophylaxis and antiretroviral treatment interventions with drug resistance

We introduce a model for HIV/AIDS which can be utilized to assess the impact of combining pre-exposure prophylaxis (PrEP) and antiretroviral drugs (ARVs) use interventions (incorporating drug resistance). Mathematical and numerical analyses are carried out to investigate the effects of the combined controls in the presence of PrEP drug resistance. Our results predict a significant decrease in the number of new HIV infections when PrEP and ARVs are concurrently implemented at high levels. The results also reveal that PrEP drug resistance has the potential to slow down or reverse the effects of PrEP, especially at low efficacy levels.

Potential impact of pre-exposure prophylaxis for female sex workers and men who have sex with men in Bangalore, India: a mathematical modelling study

INTRODUCTION

In Bangalore, new HIV infections of female sex workers and men who have sex with men continue to occur, despite high condom use. Pre-exposure prophylaxis (PrEP) has high anti-HIV efficacy for men who have sex with men. PrEP demonstration projects are underway amongst Indian female sex workers. We estimated the impact and efficiency of prioritizing PrEP to female sex workers and/or men who have sex with men in Bangalore.

METHODS

A mathematical model of HIV transmission and treatment for female sex workers, clients, men who have sex with men and low-risk groups was parameterized and fitted to Bangalore data. The proportion of transmission attributable (population attributable fraction) to commercial sex and sex between men was calculated. PrEP impact (infections averted, life-years gained) and efficiency (life-years gained/infections averted per 100 person-years on PrEP) were estimated for different levels of PrEP adherence, coverage and prioritization strategies (female sex workers, high-risk men who have sex with men, both female sex workers and high-risk men who have sex with men, or female sex workers with lower condom use), under current conditions and in a scenario with lower baseline condom use amongst key populations.

RESULTS

Population attributable fractions for commercial sex and sex between men have declined over time, and they are predicted to account for 19% of all new infections between 2016 and 2025. PrEP could prevent a substantial proportion of infections amongst female sex workers and men who have sex with men in this setting (23%/27% over 5/10 years, with 60% coverage and 50% adherence), which could avert 2.9%/4.3% of infections over 5/10 years in the whole Bangalore population. Impact and efficiency in the whole population was greater if female sex workers were prioritized. Efficiency increased, but impact decreased, if only female sex workers with lower condom use were given PrEP. Greater impact and efficiency was predicted for the scenario with lower condom use.

CONCLUSIONS

PrEP could be beneficial for female sex workers and men who have sex with men in Bangalore, and give some benefits in the general population, especially in similar settings with lower condom use levels.

How Much Do We Know about Drug Resistance Due to PrEP Use? Analysis of Experts' Opinion and Its Influence on the Projected Public Health Impact

BACKGROUND

Randomized controlled trials reported that pre-exposure prophylaxis (PrEP) with tenofovir and emtricitabine rarely selects for drug resistance. However, drug resistance due to PrEP is not completely understood. In daily practice, PrEP will not be used under the well-controlled conditions available in the trials, suggesting that widespread use of PrEP can result in increased drug resistance.

METHODS

We surveyed expert virologists with questions about biological assumptions regarding drug resistance due to PrEP use. The influence of these assumptions on the prevalence of drug resistance and the fraction of HIV transmitted resistance was studied with a mathematical model. For comparability, 50% PrEP-coverage of and 90% per-act efficacy of PrEP in preventing HIV acquisition are assumed in all simulations.

RESULTS

Virologists disagreed on the following: the time until resistance emergence (range: 20-180 days) in infected PrEP users with breakthrough HIV infections; the efficacy of PrEP against drug-resistant HIV (25%-90%); and the likelihood of resistance acquisition upon transmission (10%-75%). These differences translate into projections of 0.6%- 1% and 3.5%-6% infected individuals with detectable resistance 10 years after introducing PrEP, assuming 100% and 50% adherence, respectively. The rate of resistance emergence following breakthrough HIV infection and the rate of resistance reversion after PrEP use is discontinued, were the factors identified as most influential on the expected resistance associated with PrEP. Importantly, 17-23% infected individuals could virologically fail treatment as a result of past PrEP use or transmitted resistance to PrEP with moderate adherence.

CONCLUSIONS

There is no broad consensus on quantification of key biological processes that underpin the emergence of PrEP-associated drug resistance. Despite this, the contribution of PrEP use to the prevalence of the detectable drug resistance is expected to be small. However, individuals who become infected despite the use of PrEP should be closely monitored due to higher risk of virological failure when initiating antiretroviral treatment in the future.

Sexual Behavior, Risk Compensation, and HIV Prevention Strategies Among Participants in the San Francisco PrEP Demonstration Project: A Qualitative Analysis of Counseling Notes

Pre-exposure prophylaxis (PrEP) is a viable HIV prevention strategy but risk compensation could undermine potential benefits. There are limited data that examine this phenomenon outside of clinical trials. We conducted a qualitative analysis of counseling notes from the San Francisco site of the US PrEP demonstration project to assess how men who have sex with men used PrEP as a prevention strategy and its impact on their sexual practices. Four major themes emerged from our analysis of 130 distinct notes associated with 26 participants. Prevention strategy decision-making was dynamic, often influenced by the context and perceived risk of a sexual encounter. Counselors noted that participants used PrEP in conjunction with other health promotion strategies like condoms, asking about HIV status of their sex partners, and seroadaptation. With few exceptions, existing risk reduction strategies were not abandoned upon initiation of PrEP. Risk-taking behavior was 'seasonal' and fluctuations were influenced by various personal, psychosocial, and health-related factors. PrEP also helped relieve anxiety regarding sex and HIV, particularly among serodiscordant partners. Understanding sexual decision-making and how PrEP is incorporated into existing prevention strategies can help inform future PrEP implementation efforts.

Data and methods to characterize the role of sex work and to inform sex work programs in generalized HIV epidemics: evidence to challenge assumptions

In the context of generalized human immunodeficiency virus (HIV) epidemics, there has been limited recent investment in HIV surveillance and prevention programming for key populations including female sex workers. Often implicit in the decision to limit investment in these epidemic settings are assumptions including that commercial sex is not significant to the sustained transmission of HIV, and HIV interventions designed to reach "all segments of society" will reach female sex workers and clients. Emerging empiric and model-based evidence is challenging these assumptions. This article highlights the frameworks and estimates used to characterize the role of sex work in HIV epidemics as well as the relevant empiric data landscape on sex work in generalized HIV epidemics and their strengths and limitations. Traditional approaches to estimate the contribution of sex work to HIV epidemics do not capture the potential for upstream and downstream sexual and vertical HIV transmission. Emerging approaches such as the transmission population attributable fraction from dynamic mathematical models can address this gap. To move forward, the HIV scientific community must begin by replacing assumptions about the epidemiology of generalized HIV epidemics with data and more appropriate methods of estimating the contribution of unprotected sex in the context of sex work.

Potential impact of multiple interventions on HIV incidence in a hyperendemic region in Western Kenya: a modelling study

BACKGROUND

Multiple prevention interventions, including early antiretroviral therapy initiation, may reduce HIV incidence in hyperendemic settings. Our aim was to predict the short-term impact of various single and combined interventions on HIV spreading in the adult population of Ndhiwa subcounty (Nyanza Province, Kenya).

METHODS

A mathematical model was used with data on adults (15-59 years) from the Ndhiwa HIV Impact in Population Survey to compare the impacts on HIV prevalence, HIV incidence rate, and population viral load suppression of various interventions. These interventions included: improving the cascade of care (use of three guidelines), increasing voluntary medical male circumcision (VMMC), and implementing pre-exposure prophylaxis (PrEP) use among HIV-uninfected women.

RESULTS

After four years, improving separately the cascade of care under the WHO 2013 guidelines and under the treat-all strategy would reduce the overall HIV incidence rate by 46 and 58 %, respectively, vs. the baseline rate, and by 35 and 49 %, respectively, vs. the implementation of the current Kenyan guidelines. With conservative and optimistic scenarios, VMMC and PrEP would reduce the HIV incidence rate by 15-25 % and 22-28 % vs. the baseline, respectively. Combining the WHO 2013 guidelines with VMMC would reduce the HIV incidence rate by 35-56 % and combining the treat-all strategy with VMMC would reduce it by 49-65 %. Combining the WHO 2013 guidelines, VMMC, and PrEP would reduce the HIV incidence rate by 46-67 %.

CONCLUSIONS

The impacts of the WHO 2013 guidelines and the treat-all strategy were relatively close; their implementation is desirable to reduce HIV spread. Combining several strategies is promising in adult populations of hyperendemic areas but requires regular, reliable, and costly monitoring.

Preexposure prophylaxis-related stigma: strategies to improve uptake and adherence - a narrative review

Despite high levels of efficacy, the implementation of preexposure prophylaxis (PrEP) as a strategy to prevent new HIV infection has been slow. Studies show that PrEP works so long as it is taken, making adherence one of the great challenges of effective PrEP implementation alongside issues of access and uptake. Given that effective PrEP use requires ongoing self-administration of pills by people at high risk of HIV acquisition, it is a strategy best understood not as simply biomedical, but as biobehavioral or biopsychosocial, meaning that that social, psychological, cultural, and structural factors all contribute to the success or failure of the intervention. The willingness of people at risk of HIV to take up and adhere to PrEP depends greatly upon social understandings - whether it is seen as effective, as a healthy option, and a socially acceptable strategy for preventing HIV. Stigma - unfavorable associations - can negatively influence the implementation of PrEP. Because it is associated with high-risk sexual activity, PrEP risks multiple stigmas that can differ according to specific cultural conditions. This includes the stigma of being related to HIV (which may also relate to other stigmas, such as homosexuality, sex work, and/or drug use) and the stigma of PrEP being an alternative to condoms (as condom use is associated with responsible sexual activity). PrEP-related stigma has emerged as a significant social harm that can arise from PrEP research participation, reported by trial participants from a range of different trial sites, different trial populations, and spanning different continents. Social marketing needs to redress PrEP-related stigmas through health promotion campaigns aimed at clinicians, HIV-affected communities, and people at high risk of HIV who might benefit from PrEP access. PrEP access needs to be reframed as a positive and responsible option to help people remain HIV-negative.

Acceptability of HIV Pre-Exposure Prophylaxis (PrEP) and Implementation Challenges Among Men Who Have Sex with Men in India: A Qualitative Investigation

This qualitative study explored the acceptability of HIV pre-exposure prophylaxis (PrEP) among MSM in India, and identified facilitators and barriers to future PrEP uptake. In 2014, we conducted 10 focus groups (n=61) among a purposive sample of diverse MSM recruited through community-based organizations in Chennai and Mumbai, and 10 key informant interviews with community leaders and health care providers. Participants' mean age was 26.1 years (SD 4.8); 62% completed secondary education, and 42% engaged in sex work. No focus group participants had heard of PrEP, but once explained, most reported they would likely use it. PrEP was alternately perceived as a 'back-up plan', a condom substitute, or a burden with concurrent condom use. Facilitators were potential for covert use, sex without condoms, and anxiety-less sex. Potential barriers emerged around stigma associated with PrEP use, fear of disclosures to one's family, wife, or male steady partner, and being labeled as HIV-positive or promiscuous by peers. Preferences emerged for intermittent rather than daily PrEP use, injectable PrEP, and free or subsidized access through community organizations or government hospitals. Key informants expressed additional concerns about risk compensation, non-adherence, and impact on ART availability for treatment. Demonstration projects are needed in India to support PrEP implementation tailored for at-risk MSM. Educational interventions for MSM should address concerns about PrEP effectiveness, side effects, and mitigate risk compensation. Community engagement may facilitate broad acceptability and challenge stigma around PrEP use. Importantly, provision of free or subsidized PrEP is necessary to making implementation feasible among low socioeconomic status MSM in India.

Correlates of condom use among female sex workers in The Gambia: results of a cross-sectional survey

Objectives. This study examined correlates of condom use among 248 female sex workers (FSW) in The Gambia.

Methods. Between July and August 2011, FSW in The Gambia who were older than 16 years of age, the age of consent in The Gambia, were recruited for the study using venue-based sampling and snowball sampling, beginning with seeds who were established clients with the Network of AIDS Services Organizations. To be eligible, FSW must have reported selling sex for money, favors, or goods in the past 12 months. Bivariate and multivariate logistic regressions were used to determine associations and the relative odds of the independent variables with condom use. Four different condom use dependent variables were used: consistent condom use in the past six months during vaginal or anal sex with all clients and partners; consistent condom use in the past month during vaginal sex with new clients; consistent condom use in the past month during vaginal sex with nonpaying partners (including boyfriends, husbands, or casual sexual partners); and condom use at last vaginal or anal sex with a nonpaying partner.

Results. Many FSW (67.34%, n = 167) reported it was not at all difficult to negotiate condom use with clients in all applicable situations, and these FSW were more likely to report consistent condom use with all clients and partners in the past 6 months (aOR 3.47, 95% CI [1.70–7.07]) compared to those perceiving any difficulty in condom negotiation. In addition, FSW were more likely to report using condoms in the past month with new clients (aOR 8.04, 95% CI [2.11–30.65]) and in the past month with nonpaying partners (aOR 2.93, 95% CI [1.09–7.89]) if they had been tested for HIV in the past year. Women who bought all their condoms were less likely than those who received all of their condoms for free (aOR 0.38, 95% CI [0.15–0.97]) to have used a condom at last vaginal or anal sex with a nonpaying partner.

Conclusions. HIV and sexually transmitted infection (STI) prevention interventions for FSW should aim to improve condom negotiation self-efficacy since women who report less difficulty negotiating condom use are more likely to use condoms with clients. Interventions should also be aimed at structural issues such as increasing access to free condoms and HIV testing since these were positively associated with condom use among FSW.

Translating PrEP effectiveness into public health impact: key considerations for decision-makers on cost-effectiveness, price, regulatory issues, distributive justice and advocacy for access

INTRODUCTION

The extraordinary feat of proving the effectiveness of oral pre-exposure prophylaxis (PrEP) in clinical trials in different populations in a variety of settings may prove to have been easier than ensuring it is used well. Decision-makers must make difficult choices to realize the promise of antiretroviral prophylaxis for their countries. This paper outlines key economic, regulatory and distributive justice issues that must be addressed for effective and acceptable PrEP implementation.

DISCUSSION

In considering the role that PrEP can play in combination prevention programmes, decision-makers must determine who can benefit most from PrEP, how PrEP can be provided safely and efficiently, and what kind of health system support will ensure successful implementation. To do this, they need contextualized information on disease burden by population, analyses of how PrEP services might best be delivered, and projections of the human resource and infrastructure requirements for each potential delivery model. There are cost considerations, varying cost-effectiveness results and regulatory challenges. The principles of ethics can inform thorny discussions about who should be prioritized for oral PrEP and how best to introduce it fairly. We describe the cost-effectiveness of PrEP in different populations at higher risk of HIV exposure, its price in low- and middle-income countries, and the current regulatory situation. We explore the principles of ethics that can inform resource allocation decision-making about PrEP anchored in distributive justice, at a time when universal access to antiretroviral treatment remains to be assured. We then highlight the role of advocacy in moving the PrEP agenda forward.

CONCLUSIONS

The time is ripe now for decisions about whether, how and for whom PrEP should be introduced into a country's HIV response. It has the potential to contribute significantly to high impact HIV prevention if it is tailored to those who can most benefit from it and if current regulatory and pricing barriers can be overcome. Advocacy at all levels can help inform decision-making and push the access agenda to avert HIV infections among those at highest risk of HIV exposure. The benefits will accrue beyond the individual level to slow HIV transmission at the population level.

Pre-exposure prophylaxis in Southern Africa: feasible or not?

INTRODUCTION

Southern and Eastern Africa bear the brunt of the AIDS epidemic, and current prevention interventions remain inadequate. Antiretroviral-based pre-exposure prophylaxis (PrEP) is gaining momentum as an effective prevention intervention.

DISCUSSION

Discussions have been started on how this strategy could be employed in Africa such that the populations most in need can be reached urgently for the greatest impact. This requires the selection of specific risk groups and service environments in which PrEP can be distributed safely and cost effectively while being mindful of any ethical issues.

CONCLUSIONS

Given the need for an integrated public health approach to this, a number of potential populations and opportunities for PrEP distribution exist and are discussed in this commentary.

Stakeholder Engagement in HIV Cure Research: Lessons Learned from Other HIV Interventions and the Way Forward

Clinical and basic science advances have raised considerable hope for achieving an HIV cure by accelerating research. This research is dominated primarily by issues about the nature and design of current and future clinical trials. Stakeholder engagement for HIV cure remains in its early stages. Our analysis examines timing and mechanisms of historical stakeholder engagement in other HIV research areas for HIV-uninfected individuals [vaccine development and pre-exposure prophylaxis (PrEP)], and HIV-infected individuals (treatment as prevention, prevention of mother-to-child transmission, and treatment of acute HIV infection) and articulate a plan for HIV cure stakeholder engagement. The experience from HIV vaccine development shows that early engagement of stakeholders helped manage expectations, mitigating the failure of several vaccine trials, while paving the way for subsequent trials. The relatively late engagement of HIV stakeholders in PrEP research may partly explain some of the implementation challenges. The treatment-related stakeholder engagement was strong and community-led from the onset and helped translation from research to implementation. We outline five steps to initiate and sustain stakeholder engagement in HIV cure research and conclude that stakeholder engagement represents a key investment in which stakeholders mutually agree to share knowledge, benefits, and risk of failure. Effective stakeholder engagement prevents misconceptions. As HIV cure research advances from early trials involving subjects with generally favorable prognosis to studies involving greater risk and uncertainty, success may depend on early and deliberate engagement of stakeholders.

Preparing for the Rollout of Pre-Exposure Prophylaxis (PrEP): A Vignette Survey to Identify Intended Sexual Behaviors among Women in Kenya and South Africa if Using PrEP

INTRODUCTION

Several clinical trials have demonstrated the efficacy of pre-exposure prophylaxis (PrEP) in reducing HIV risk. One concern with introducing PrEP is whether users will engage in riskier sexual behaviors.

METHODS

We assessed the effect that PrEP may have on sexual risk behaviors by administering a survey to 799 women in Bondo, Kenya, and Pretoria, South Africa. Participants were asked about their sexual behavior intentions twice--once as if they were taking PrEP and once as if they were not taking PrEP--within four risk situations (vignettes). They responded using a 5-point ordinal scale. We used a series of linear mixed effects models with an unstructured residual covariance matrix to estimate the between- and within-subject differences in the mean likelihood of engaging in risky sexual behavior across the PrEP and non-PrEP contexts. We also calculated the total percentage of participants who reported a greater likelihood of engaging in risky sexual behavior if taking PrEP than if not taking PrEP, by vignette.

RESULTS

We found statistically significant differences in the mean likelihood of engaging in risky sexual behavior with the between-subject comparison (-0.17, p < 0.01) and with the within-subject comparison (-0.31, p < 0.001). Depending on the vignette, 27% to 40% of participants reported a greater likelihood of engaging in risky sexual behavior if taking PrEP than if not taking PrEP.

CONCLUSIONS

Our findings indicate that modest increases in risky sexual behavior could occur with PrEP. Although responses from the majority of participants suggest they would not be more likely to engage in risky sexual behavior if they took PrEP, a substantial proportion might. Programs rolling out PrEP should be prepared to assist similar women in making informed choices about reducing their risk of HIV and about their sexual health beyond HIV prevention.

Targeting pre-exposure prophylaxis among men who have sex with men in the United States and Peru: partnership types, contact rates, and sexual role

BACKGROUND

We aim to identify optimal strategies for deploying pre-exposure prophylaxis among men who have sex with men (MSM) in the United States and Peru to maximize population-level effectiveness in an efficient manner. We use epidemic models to simulate the impact of targeting strategies. Most studies have focused on targeting either the general population or high-risk MSM. Alternative strategies, including serodiscordant couples, may better balance effectiveness and efficiency.

METHODS

We use dynamic stochastic sexual network models based on exponential-family random graph modeling, parameterized from behavioral surveys of MSM in the United States and Peru. These models represent main partnerships and casual contacts separately, permitting modeling of interventions targeting men whose risk derives from combinations of relational types. We also model varying rates of uptake and adherence to pre-exposure prophylaxis (PrEP). We assess sensitivity of results to risk compensation through increases in condomless casual contacts and condomless sex in main partnerships.

RESULTS

Targeting all men who are not exclusively insertive has the largest impact on HIV incidence, but targeting only those with high levels of casual activity yields comparable results using fewer person-years on PrEP. The effect is robust to risk compensation in the United States, but less so in Peru. Targeting serodiscordant main partnerships does not significantly impact incidence, but requires fewer person-years on PrEP per infection averted than other strategies.

CONCLUSIONS

PrEP could be effective in reducing new infections at the population level in both settings. Serodiscordant partnerships are an attractive component of a targeting program, but targeting should include other high-risk men.

An action agenda for HIV and sex workers

The women, men, and transgender people who sell sex globally have disproportionate risks and burdens of HIV in countries of low, middle, and high income, and in concentrated and generalised epidemic contexts. The greatest HIV burdens continue to be in African female sex workers. Worldwide, sex workers still face reduced access to needed HIV prevention, treatment, and care services. Legal environments, policies, police practices, absence of funding for research and HIV programmes, human rights violations, and stigma and discrimination continue to challenge sex workers' abilities to protect themselves, their families, and their sexual partners from HIV. These realities must change to realise the benefits of advances in HIV prevention and treatment and to achieve global control of the HIV pandemic. Effective combination prevention and treatment approaches are feasible, can be tailored for cultural competence, can be cost-saving, and can help to address the unmet needs of sex workers and their communities in ways that uphold their human rights. To address HIV in sex workers will need sustained community engagement and empowerment, continued research, political will, structural and policy reform, and innovative programmes. But such actions can and must be achieved for sex worker communities everywhere.

Combination HIV prevention for female sex workers: what is the evidence?

Sex work occurs in many forms and sex workers of all genders have been affected by HIV epidemics worldwide. The determinants of HIV risk associated with sex work occur at several levels, including individual biological and behavioural, dyadic and network, and community and social environmental levels. Evidence indicates that effective HIV prevention packages for sex workers should include combinations of biomedical, behavioural, and structural interventions tailored to local contexts, and be led and implemented by sex worker communities. A model simulation based on the South African heterosexual epidemic suggests that condom promotion and distribution programmes in South Africa have already reduced HIV incidence in sex workers and their clients by more than 70%. Under optimistic model assumptions, oral pre-exposure prophylaxis together with test and treat programmes could further reduce HIV incidence in South African sex workers and their clients by up to 40% over a 10-year period. Combining these biomedical approaches with a prevention package, including behavioural and structural components as part of a community-driven approach, will help to reduce HIV infection in sex workers in different settings worldwide.

Pre-exposure prophylaxis of HIV: A right way to go or a long way to go?

Antiretroviral drugs are being tried as candidates for the pre-exposure prophylaxis (PrEP) against HIV for a considerable period, due to their potential for immediate inhibition of viral replication. Discrepancies in the findings called for a critical review of the relevant efforts and their outcomes. A systematic literature search identified 143 eligible articles of which only 5 reported complete findings while another 11 were still on-going. Observed moderate efficacy and good safety profile seemed to identify PrEP as a promising step for minimizing the spread of HIV to relatively unaffected population and controlling the epidemic among high risk population groups. But the duration of this efficacy was found to depend heavily on the availability, adherence and other related issues like cost, political commitment, ethical consideration etc. To prevent potential cultural and behavioral modifications, proper pre-administration counseling also seemed critical for the success of PrEP as a cost-effective intervention with adequate coverage.

HIV pre-exposure prophylaxis for people who inject drugs: a review of current results and an agenda for future research

Introduction

Studies examining the use of pre-exposure prophylaxis (PrEP) to prevent HIV transmission among people who inject drugs (PWIDs) have not been adequately summarized. Recently, the Bangkok Tenofovir Study has shown that PrEP may be effective at reducing new HIV infections among this high-risk group. This randomized controlled trial was the first study to specifically examine the efficacy of PrEP among PWIDs. In this review, we present the current state of evidence regarding the use of PrEP to prevent HIV infection in PWID populations, and set an agenda for future research to inform the most effective implementation of PrEP in the context of existing evidence-based HIV prevention strategies.

Discussion

Despite positive trial results confirming that PrEP may prevent HIV transmission among PWIDs, there remain many questions regarding the interpretation of these results, as well as obstacles to the implementation of PrEP regimens within highly diverse drug-using communities. Aside from the Bangkok Tenofovir Study, we identified only one other published study that has collected empirical data to inform the use of PrEP among PWIDs. The large gap in research regarding the use and implementation of PrEP for PWIDs signals the need for further research and attention.

Conclusions

We recommend that future research efforts focus on elucidating the generalizability of the Bangkok Tenofovir Study results in other injection drug–using populations, examining the willingness of PWIDs to use PrEP in diverse contexts, identifying barriers to adherence to PrEP regimens and determining the most effective ways to implement PrEP programmes within the context of existing evidence-based prevention strategies, including opioid substitution therapy and needle and syringe distribution programmes.

Global evidence reaffirms the case for routine HPV and potential HIV adolescent vaccination in South Africa

ABSTRACT: 

The availability of two prophylactic HPV vaccines, coupled with a potential prophylactic HIV vaccine delivered to adolescents through a school-based sexual and reproductive health platform represents a potentially significant, potent long-term primary prevention strategy against two sexually transmitted infections: HPV and HIV infection within a highly susceptible group. South Africa has earmarked the re-engineering of school health services. This initiative ensures a ‘health presence in every school’ focused on developing a social, sexual and reproductive health platform within secondary schools addressing HIV/AIDS prevention, teenage pregnancies and social concerns such as drug abuse. Despite this opportunistic platform for HIV and HPV vaccines introduction among adolescents, much work remains to overcome existing ethical and financial and programmatic barriers.

Personalized Biobehavioral HIV Prevention for Women and Adolescent Girls

Background:

Women and adolescent girls bear a significant burden of the global HIV pandemic. Both behavioral and biomedical prevention approaches have been shown to be effective. In order to foster the most effective combination HIV-prevention approaches for women and girls, it is imperative to understand the unique biological, social, and structural considerations that increase vulnerability to acquiring HIV within this population.

Primary Study Objective:

The purpose of this article is to propose novel ideas for personalized biobehavioral HIV prevention for women and adolescent girls. The central argument is that we must transcend unilevel solutions for HIV prevention toward comprehensive, multilevel combination HIV prevention packages to actualize personalized biobehavioral HIV prevention. Our hope is to foster transnational dialogue among researchers, practitioners, educators, and policy makers toward the actualization of the proposed recommendations.

Methods:

We present a commentary organized to review biological, social, and structural factors that increase vulnerability to HIV acquisition among women and adolescent girls. The overview is followed by recommendations to curb HIV rates in the target population in a sustainable manner.

Results:

The physiology of the lower female reproductive system biologically increases HIV risk among women and girls. Social (eg, intimate partner violence) and structural (eg, gender inequality) factors exacerbate this risk by increasing the likelihood of viral exposure. Our recommendations for personalized biobehavioral HIV prevention are to (1) create innovative mechanisms for personalized HIV risk—reduction assessments; (2) develop mathematical models of local epidemics; (3) prepare personalized, evidence-based combination HIV risk—reduction packages; (4) structure gender equity into society; and (5) eliminate violence (both physical and structural) against women and girls.

Conclusions:

Generalized programs and interventions may not have universal, transnational, and crosscultural implications. Personalized biobehavioral strategies are needed to comprehensively address vulnerabilities at biological, social, and structural levels.

No evidence of sexual risk compensation in the iPrEx trial of daily oral HIV preexposure prophylaxis

Objective

Preexposure prophylaxis (PrEP) with emtricitabine/tenofovir disoproxil fumarate (FTC/TDF) reduced HIV acquisition in the iPrEx trial among men who have sex with men and transgender women. Self-reported sexual risk behavior decreased overall, but may be affected by reporting bias. We evaluated potential risk compensation using biomarkers of sexual risk behavior.

Design and methods

Sexual practices were assessed at baseline and quarterly thereafter; perceived treatment assignment and PrEP efficacy beliefs were assessed at 12 weeks. Among participants with ≥1 follow-up behavioral assessment, sexual behavior, syphilis, and HIV infection were compared by perceived treatment assignment, actual treatment assignment, and perceived PrEP efficacy.

Results

Overall, acute HIV infection and syphilis decreased during follow-up. Compared with participants believing they were receiving placebo, participants believing they were receiving FTC/TDF reported more receptive anal intercourse partners prior to initiating drug (12.8 vs. 7.7, P = 0.04). Belief in receiving FTC/TDF was not associated with an increase in receptive anal intercourse with no condom (ncRAI) from baseline through follow-up (risk ratio [RR] 0.9, 95% confidence interval [CI]: 0.6–1.4; P = 0.75), nor with a decrease after stopping study drug (RR 0.8, 95% CI: 0.5–1.3; P = 0.46). In the placebo arm, there were trends toward lower HIV incidence among participants believing they were receiving FTC/TDF (incidence rate ratio [IRR] 0.8, 95% CI: 0.4–1.8; P = 0.26) and also believing it was highly effective (IRR 0.5, 95% CI: 0.1–1.7; P = 0.12).

Conclusions

There was no evidence of sexual risk compensation in iPrEx. Participants believing they were receiving FTC/TDF had more partners prior to initiating drug, suggesting that risk behavior was not a consequence of PrEP use.

Preexposure prophylaxis will have a limited impact on HIV-1 drug resistance in sub-Saharan Africa: a comparison of mathematical models

BACKGROUND

Preexposure prophylaxis (PrEP) with tenofovir and emtricitabine can prevent new HIV-1 infections, but there is a concern that use of PrEP could increase HIV drug resistance resulting in loss of treatment options. We compared standardized outcomes from three independent mathematical models simulating the impact of PrEP on HIV transmission and drug resistance in sub-Saharan African countries.

METHODS

All models assume that people using PrEP receive an HIV test every 3-6 months. The models vary in structure and parameter choices for PrEP coverage, effectiveness of PrEP (at different adherence levels) and the rate with which HIV drug resistance emerges and is transmitted.

RESULTS

The models predict that the use of PrEP in conjunction with antiretroviral therapy will result in a lower prevalence of HIV than when only antiretroviral therapy is used. With or without PrEP, all models suggest that HIV drug resistance will increase over the next 20 years due to antiretroviral therapy. PrEP will increase the absolute prevalence of drug resistance in the total population by less than 0.5% and amongst infected individuals by at most 7%. Twenty years after the introduction of PrEP, the majority of drug-resistant infections is due to antiretroviral therapy (50-63% across models), whereas 40-50% will be due to transmission of drug resistance, and less than 4% to the use of PrEP.

CONCLUSION

HIV drug resistance resulting from antiretroviral therapy is predicted to far exceed that resulting from PrEP. Concern over drug resistance should not be a reason to limit the use of PrEP.

Analytic review of modeling studies of ARV Based PrEP interventions reveals strong influence of drug-resistance assumptions on the population-level effectiveness

Background

Four clinical trials have shown that oral and topical pre-exposure prophylaxis (PrEP) based on tenofovir may be effective in preventing HIV transmission. The expected reduction in HIV transmission and the projected prevalence of drug resistance due to PrEP use vary significantly across modeling studies as a result of the broad spectrum of assumptions employed. Our goal is to quantify the influence of drug resistance assumptions on the predicted population-level impact of PrEP.

Methods

All modeling studies which evaluate the impact of oral or topical PrEP are reviewed and key assumptions regarding mechanisms of generation and spread of drug-resistant HIV are identified. A dynamic model of the HIV epidemic is developed to assess and compare the impact of oral PrEP using resistance assumptions extracted from published studies. The benefits and risks associated with ten years of PrEP use are evaluated under identical epidemic, behavioral and intervention conditions in terms of cumulative fractions of new HIV infections prevented, resistance prevalence among those infected with HIV, and fractions of infections in which resistance is transmitted.

Results

Published models demonstrate enormous variability in resistance-generating assumptions and uncertainty in parameter values. Depending on which resistance parameterization is used, a resistance prevalence between 2% and 44% may be expected if 50% efficacious oral PrEP is used consistently by 50% of the population over ten years. We estimated that resistance may be responsible for up to a 10% reduction or up to a 30% contribution to the fraction of prevented infections predicted in different studies.

Conclusions

Resistance assumptions used in published studies have a strong influence on the projected impact of PrEP. Modelers and virologists should collaborate toward clarifying the set of resistance assumptions biologically relevant to the PrEP products which are already in use or soon to be added to the arsenal against HIV.

Sexual risk behavior among HIV-uninfected men who have sex with men participating in a tenofovir preexposure prophylaxis randomized trial in the United States

OBJECTIVE

To evaluate for changes in sexual behaviors associated with daily pill use among men who have sex with men (MSM) participating in a preexposure prophylaxis trial.

DESIGN

Randomized, double-blind, placebo-controlled trial. Participants were randomized 1:1:1:1 to receive tenofovir disoproxil fumarate or placebo at enrollment or after a 9-month delay and followed for 24 months.

METHODS

Four hundred HIV-negative MSM reporting anal sex with a man in the past 12 months and meeting other eligibility criteria enrolled in San Francisco, Atlanta, and Boston. Sexual risk was assessed at baseline and quarterly visits using Audio Computer-Assisted Self-Interview. The association of pill taking with sexual behavior was evaluated using logistic and negative-binomial regressions for repeated measures.

RESULTS

Overall indices of behavioral risk declined or remained stable during follow-up. Mean number of partners and proportion reporting unprotected anal sex declined during follow-up (P < 0.05), and mean unprotected anal sex episodes remained stable. During the initial 9 months, changes in risk practices were similar in the group that began pills immediately vs. those in the delayed arm. These indices of risk did not differ significantly after initiation of pill use in the delayed arm or continuation of study medication in the immediate arm. Use of poppers, amphetamines, and sexual performance-enhancing drugs were independently associated with one or more indices of sexual risk.

CONCLUSIONS

There was no evidence of risk compensation among HIV-uninfected MSM in this clinical trial. Monitoring for risk compensation should continue now that preexposure prophylaxis has been shown to be efficacious in MSM and other populations and will be provided in open-label trials and other contexts.

Microbicides for the prevention of sexually transmitted HIV infection

The impetus for, and efforts in the past 20 years toward a women-initiated method for preventing sexual transmission of HIV has been previously well described. To date, four classes of topical agents categorized by mechanism of action as: surfactants, buffers, cell entry blockers and antiretroviral agents have undergone advanced clinical testing. Thus far, only coitally linked use of 1% tenofovir gel has demonstrated moderate effectiveness in preventing HIV and HSV-2 infection and has generated renewed hope for microbicide development. Studies of new antiviral agents, novel delivery mechanisms and combination/multipurpose products that address challenges of adherence and enhance the effectiveness of tenofovir gel are already underway to further enhance sexual and reproductive health needs of men and women and efforts to prevent HIV infection.

Sexual behaviour of heterosexual men and women receiving antiretroviral pre-exposure prophylaxis for HIV prevention: a longitudinal analysis

BACKGROUND

Scarce data are available to assess sexual behaviour of individuals using antiretroviral pre-exposure prophylaxis for HIV prevention. Increased sexual risk taking by individuals using effective HIV prevention strategies, like pre-exposure prophylaxis, could offset the benefits of HIV prevention. We studied whether the use of pre-exposure prophylaxis in HIV-uninfected men and women in HIV-serodiscordant couples was associated with increased sexual risk behaviour.

METHODS

We undertook a longitudinal analysis of data from the Partners PrEP Study, a double-blind, randomised, placebo-controlled trial of daily oral pre-exposure prophylaxis among HIV-uninfected partners of heterosexual HIV-serodiscordant couples (n=3163, ≥18 years of age). Efficacy for HIV prevention was publicly reported in July 2011, and participants continued monthly follow-up thereafter. We used regression analyses to compare the frequency of sex-unprotected by a condom-during the 12 months after compared with the 12 months before July 2011, to assess whether knowledge of pre-exposure prophylaxis efficacy for HIV prevention caused increased sexual risk behaviour.

RESULTS

We analysed 56 132 person-months from 3024 HIV-uninfected individuals (64% male). The average frequency of unprotected sex with the HIV-infected study partner was 59 per 100 person-months before unmasking versus 53 after unmasking; we recorded no immediate change (p=0·66) or change over time (p=0·25) after July, 2011. We identified a significant increase in unprotected sex with outside partners after July, 2011, but the effect was small (average of 6·8 unprotected sex acts per year vs 6·2 acts in a predicted counterfactual scenario had patients remained masked, p=0·04). Compared with before July, 2011, we noted no significant increase in incident sexually transmitted infections or pregnancy after July, 2011.

INTERPRETATION

Pre-exposure prophylaxis, provided as part of a comprehensive prevention package, might not result in substantial changes in risk-taking sexual behaviour by heterosexual couples.

FUNDING

The Bill & Melinda Gates Foundation and the US National Institute of Mental Health.

Evolving uses of oral reverse transcriptase inhibitors in the HIV-1 epidemic: from treatment to prevention

The HIV epidemic continues unabated, with no highly effective vaccine and no cure. Each new infection has significant economic, social and human costs and prevention efforts are now as great a priority as global antiretroviral therapy (ART) scale up. Reverse transcriptase inhibitors, the first licensed class of ART, have been at the forefront of treatment and prevention of mother to child transmission over the past two decades. Now, their use in adult prevention is being extensively investigated. We describe two approaches: treatment as prevention (TasP) - the use of combination ART (2NRTI and 1NNRTI) following HIV diagnosis to limit transmission and pre-exposure prophylaxis (PrEP) –the use of single or dual oral agents prior to sexual exposure. Prevention of mother-to-child transmission using NRTI has been highly successful, though does not involve sustained use of NRTI to limit transmission. Despite theoretical and preliminary support for TasP and PrEP, data thus far indicate that adherence, retention in care and late diagnosis are the major barriers to their successful, sustained implementation. Future advances in drug technologies will be needed to overcome the issue of drug adherence, through development of drugs that involve both less frequent dosing as well as reduced toxicity, possibly through specific targeting of infected cells.

The promise of pre-exposure prophylaxis with antiretroviral drugs to prevent HIV transmission: a review

PURPOSE OF REVIEW

Public health experts are wrestling with how to translate recent scientific findings from pre-exposure prophylaxis (PrEP) effectiveness trials into real-world programmes. This review summarizes clinical trial findings on oral and topical PrEP, discusses how decision-makers can evaluate the place of PrEP within combination prevention and highlights anticipated developments that could be important in future HIV-prevention strategies.

RECENT FINDINGS

PrEP taken daily as oral tablets to create systemic protection has been found to be effective in the Pre-Exposure Prophylaxis Initiative (iPrEx), Partners' PrEP and TDF2 trials, but not in Fem-PrEP or the Vaginal and Oral Interventions to Control the Epidemic (VOICE) tenofovir arm. Tenofovir gel for topical protection was effective in CAPRISA 004 when used peri-coitally but not in VOICE with daily use. These findings underscore the importance of adherence to achieve adequate drug levels and the potential additive role of PrEP within combination prevention. Pivotal phase III trials are underway of the dapivirine ring, whereas phase I trials of injectable formulations show promise.

SUMMARY

Antiretroviral-based HIV-prevention programmes should be tailored to those most likely to be adherent, providing them with state-of-the-art counselling and support to achieve high adherence during the time period of use. Long-acting products, if found well tolerated and effective, could be ideal for overcoming adherence challenges.