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Impact of the Centers for Disease Control's HIV Preexposure Prophylaxis Guidelines for Men Who Have Sex With Men in the United States
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Implementation of CDC guidelines for PrEP would result in significant and sustained declines in HIV prevalence and incidence among MSM in the United States, according to our modeling study. This assumes fixed sexual behaviors, clinical care utilization patterns, and other factors potentially influencing HIV transmission dynamics that could potentially reduce the prevention benefits of PrEP. Under the 3 behavioral indications for PrEP within the guidelines, 40% coverage of indicated MSM, and 62% high adherence, 1162 new infections would be averted per 100 000 person-years at risk, representing 33% of cases expected over the next decade. This study therefore provides strong support for the CDC HIV prevention guidelines from a modeling framework.
Journal of Infectious Diseases Advance Access published July 14, 2016 Samuel M. Jenness,1 Steven M. Goodreau,4 Eli Rosenberg,1 Emily N. Beylerian,5 Karen W. Hoover,3 Dawn K. Smith,3 and Patrick Sullivan1,2 Departments of 1Epidemiology, and 2Global Health, Emory University, and 3Division of HIV/AIDS Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia; 4Department of Anthropology,and 5Center for Studies in Demography and Ecology, University of Washington, Seattle
Preexposure prophylaxis (PrEP) is effective for preventing human immunodeficiency virus (HIV) infection among men who have sex with men (MSM) within trial settings. Population impact will depend on clinical indications for PrEP initiation, coverage levels, and drug adherence. No modeling studies have estimated the impact of clinical practice guidelines for PrEP issued by the Centers for Disease Control and Prevention (CDC).
Methods. Mathematical models of HIV transmission among MSM were used to estimate the percentage of infections averted (PIA) and the number needed to treat (NNT) under behavioral indications of the CDC's PrEP guidelines. We modeled the contribution of these indications while varying treatment coverage and adherence.
Results. At 40% coverage of indicated MSM over the next decade, application of CDC guidelines would avert 1162 infections per 100 000 person-years, 33.0% of expected infections. The predicted NNT for the guidelines would be 25. Increasing coverage and adherence jointly raise the PIA, but reductions to the NNT were associated with better adherence only.
Conclusions. Implementation of CDC PrEP guidelines would result in strong and sustained reductions in HIV incidence among MSM in the United States. The guidelines strike a good balance between epidemiological impact (PIA) and efficiency (NNT) at plausible scale-up levels. Adherence counseling could maximize public health investment in PrEP by decreasing the NNT.

Table 2 provides the primary results for each behavioral indication and the joint union of those indications, assuming 40% coverage of indicated MSM and 62% high adherence among those covered. Implementing PrEP consistent with CDC guidelines under these assumptions resulted in a monotonic decline in HIV prevalence and incidence. Under the best-performing joint scenario for the guidelines' indications (scenario J2), PrEP would avert 33% of new infections among MSM over the next 10 years. This would require treating 25 uninfected MSM for 1 year per infection averted.
INTRODUCTION -The efficacy of daily oral antiretroviral preexposure prophylaxis (PrEP) for the prevention of human immunodeficiency virus (HIV) infection was established in several randomized controlled trials (RCTs), including the iPrEx study that tested the tenofovir disoproxil fumarate and emtricitabine formulation among men who have sex with men (MSM) [1]. Intent-to-treat analyses estimated a prevention benefit of 44%, with efficacy at 73% among those with high self-reported adherence and 92% among those with serum-detectable drug levels [2]. Poor adherence had been a problem in establishing efficacy of PrEP in some RCTs [3], but subsequent demonstration studies have found stronger adherence in open-label settings [4, 5].
In response to these trial results, the US Food and Drug Administration approved a label indication for the prescription of Truvada for PrEP among uninfected persons at high risk of infection [6], and the Centers for Disease Control and Prevention (CDC) subsequently released guidelines for its use in clinical practice [7]. In these guidelines, PrEP is indicated for MSM who are at “substantial risk” of infection, defined primarily by 3 behavioral criteria: unprotected (ie, condomless) anal intercourse (UAI) in HIV status–unknown monogamous partnerships, UAI outside a monogamous partnership, and anal intercourse (AI) in a known-serodiscordant partnership. Sexually transmitted infection diagnoses, another criterion, are considered biological indications of risky sexual activity. For each criterion, clinicians should query these indications over the prior 6 months; any events during that “risk window” trigger a possible indication for PrEP. The CDC supports PrEP use as part of a comprehensive prevention plan that includes other biomedical and behavioral prevention strategies.
The guidelines' criteria were devised based on analyses of RCT data [8]. However, persons eligible for and willing to participate in RCTs may not represent the broader target population for interventions [9]. Public PrEP programs also may not replicate the extensive ancillary risk reduction and adherence counseling components within research settings [10]. It is therefore critical to understand the impact of different schemes for targeting PrEP on population-level HIV incidence. Mathematical models provide one approach to estimating PrEP impact [11, 12], but PrEP models of MSM to date have modeled uptake schemes that differ from the CDC guidelines [13] or use static modeling approaches that do not represent MSM sexual partnerships relevant for the guidelines' behavioral indications [14]. A model-based investigation of the CDC guidelines will be helpful for state and local public health officials seeking to estimate the impact of including PrEP within a comprehensive HIV prevention plan.
In this study, we model HIV transmission dynamics among MSM to estimate the proportion of infections averted, the number needed to treat (NNT) with PrEP to prevent 1 new infection, and related epidemiological outcomes after implementing PrEP according to the CDC guidelines. The goal is to quantify reductions in incidence associated with individual guideline indications, separately and jointly, and to explore the impact of varying conditions of coverage and adherence patterns during the next 10 years.
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