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Baeten J.M.,University of Washington | Haberer J.E.,Massachusetts General Hospital | Haberer J.E.,Harvard University | Liu A.Y.,Bridge HIV | And 2 more authors.
Journal of Acquired Immune Deficiency Syndromes

Preexposure prophylaxis (PrEP), in which HIV-uninfected persons with ongoing HIV risk use antiretroviral medications to reduce their risk of acquiring HIV infection, is an efficacious and promising new HIV prevention strategy. The past 2 years have seen significant new advances in knowledge regarding PrEP, including definitive demonstration that PrEP reduces the risk of HIV acquisition, regulatory approval of combination oral emtricitabine/ tenofovir disoproxil fumarate (FTC/TDF) as the first PrEP agent with a label indication for sexual HIV prevention, and the development of normative guidance for clinical prescribing of PrEP. In PrEP clinical trials, HIV protection was strongly correlated with PrEP adherence; therefore, understanding and supporting adherence to PrEP are key to maximizing its public health impact. As would be expected for any new HIV prevention approach, questions remain, including how to motivate uptake of and sustain adherence to PrEP for HIV prevention in high-risk populations, how much use is sufficient to achieve HIV protection, and the potential of "next-generation" PrEP agents to improve this effective prevention strategy. At this important transition point-from demonstration of efficacy in clinical trials to thinking about implementation and effectiveness- this review addresses where we have been and where we are going with PrEP for HIV prevention. Copyright © 2013 by Lippincott Williams & Wilkins. Source

Scott H.M.,Bridge HIV | Klausner J.D.,University of California at Los Angeles
AIDS Research and Therapy

Pre-Exposure Prophylaxis (PrEP) has shown high efficacy in preventing human immunodeficiency virus (HIV) infection among men who have sex with men (MSM) in several large clinical trials, and more recently in "real world" reports of clinical implementation and a PrEP demonstration project. Those studies also demonstrated high bacterial sexually transmitted infection (STI) incidence and raised the discussion of how PrEP may impact STI control efforts, especially in the setting of increasing Neisseria gonorrhoeae antimicrobial resistance and the increase in syphilis cases among MSM. Here, we discuss STIs as a driver of HIV transmission risk among MSM, and the potential opportunities and challenges for STI control afforded by expanded PrEP implementation among high-risk MSM. © 2016 Scott and Klausner. Source

Goodreau S.M.,University of Washington | Carnegie N.B.,Harvard University | Vittinghoff E.,University of California at San Francisco | Lama J.R.,Asociacion Civil IMPACTA Salud y Educacion | And 5 more authors.

In this work, we estimate the proportions of transmissions occurring in main vs. casual partnerships, and by the sexual role, infection stage, and testing and treatment history of the infected partner, for men who have sex with men (MSM) in the US and Peru. We use dynamic, stochastic models based in exponential random graph models (ERGMs), obtaining inputs from multiple large-scale MSM surveys. Parallel main partnership and casual sexual networks are simulated. Each man is characterized by age, race, circumcision status, sexual role behavior, and propensity for unprotected anal intercourse (UAI); his history is modeled from entry into the adult population, with potential transitions including HIV infection, detection, treatment, AIDS diagnosis, and death. We implemented two model variants differing in assumptions about acute infectiousness, and assessed sensitivity to other key inputs. Our two models suggested that only 4-5% (Model 1) or 22-29% (Model 2) of HIV transmission results from contacts with acute-stage partners; the plurality (80-81% and 49%, respectively) stem from chronic-stage partners and the remainder (14-16% and 27-35%, respectively) from AIDS-stage partners. Similar proportions of infections stem from partners whose infection is undiagnosed (24-31%), diagnosed but untreated (36-46%), and currently being treated (30-36%). Roughly one-third of infections (32-39%) occur within main partnerships. Results by country were qualitatively similar, despite key behavioral differences; one exception was that transmission from the receptive to insertive partner appears more important in Peru (34%) than the US (21%). The broad balance in transmission contexts suggests that education about risk, careful assessment, pre-exposure prophylaxis, more frequent testing, earlier treatment, and risk-reduction, disclosure, and adherence counseling may all contribute substantially to reducing the HIV incidence among MSM in the US and Peru. © 2012 Goodreau et al. Source

Buchbinder S.P.,Bridge HIV | Buchbinder S.P.,University of California at San Francisco | Glidden D.V.,University of California at San Francisco | Liu A.Y.,Bridge HIV | And 8 more authors.
The Lancet Infectious Diseases

Background: For maximum effect pre-exposure prophylaxis should be targeted to the subpopulations that account for the largest proportion of infections (population-attributable fraction [PAF]) and for whom the number needed to treat (NNT) to prevent infection is lowest. We aimed to estimate the PAF and NNT of participants in the iPrEx (Pre-Exposure Prophylaxis Initiative) trial. Methods: The iPrEx study was a randomised controlled efficacy trial of pre-exposure prophylaxis with coformulated tenofovir disoproxil fumarate and emtricitabine in 2499 men who have sex with men (MSM) and transgender women. Participants aged 18 years or older who were male at birth were enrolled from 11 trial sites in Brazil, Ecuador, Peru, South Africa, Thailand, and the USA. Participants were randomly assigned (1:1) to receive either a pill with active pre-exposure prophylaxis or placebo, taken daily. We calculated the association between demographic and risk behaviour during screening and subsequent seroconversion among placebo recipients using a Poisson model, and we calculated the PAF and NNT for risk behaviour subgroups. The iPrEx trial is registered with ClinicalTrials.gov, NCT00458393. Findings: Patients were enrolled between July 10, 2007, and Dec 17, 2009, and were followed up until Nov 21, 2010. Of the 2499 MSM and transgender women in the iPrEx trial, 1251 were assigned to pre-exposure prophylaxis and 1248 to placebo. 83 of 1248 patients in the placebo group became infected with HIV during follow-up. Participants reporting receptive anal intercourse without a condom seroconverted significantly more often than those reporting no anal sex without a condom (adjusted hazard ratio [AHR] 5·11, 95% CI 1·55-16·79). The overall PAF for MSM and transgender women reporting receptive anal intercourse without a condom was 64% (prevalence 60%). Most of this risk came from receptive anal intercourse without a condom with partners with unknown serostatus (PAF 53%, prevalence 54%, AHR 4·76, 95% CI 1·44-15·71); by contrast, the PAF for receptive anal intercourse without a condom with an HIV-positive partner was 1% (prevalence 1%, AHR 7·11, 95% CI 0·70-72·75). The overall NNT per year for the cohort was 62 (95% CI 44-147). NNTs were lowest for MSM and transgender women self-reporting receptive anal intercourse without a condom (NNT 36), cocaine use (12), or a sexually transmitted infection (41). Having one partner and insertive anal sex without a condom had the highest NNTs (100 and 77, respectively). Interpretation: Pre-exposure prophylaxis may be most effective at a population level if targeted toward MSM and transgender women who report receptive anal intercourse without a condom, even if they perceive their partners to be HIV negative. Substance use history and testing for STIs should also inform individual decisions to start pre-exposure prophylaxis. Consideration of the PAF and NNT can aid in discussion of the benefits and risks of pre-exposure prophylaxis with MSM and transgender women. Funding: National Institute of Allergy and Infectious Diseases and the Bill & Melinda Gates Foundation. © 2014 Elsevier Ltd. Source

Carlo Hojilla J.,University of California at San Francisco | Koester K.A.,University of California at San Francisco | Cohen S.E.,Disease Prevention and Control | Cohen S.E.,University of California at San Francisco | And 2 more authors.
AIDS and Behavior

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. © 2015, Springer Science+Business Media New York. Source

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