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Fact Sheet

PrEP: A New Tool for HIV Prevention

August 2012

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Ongoing and Planned PrEP Trials

Injection Drug Users

CDC is sponsoring the only clinical trial of PrEP among injection drug users (IDUs), the Bangkok Tenofovir Study. The study, being conducted in Thailand, is assessing the efficacy of PrEP with daily oral tenofovir alone to prevent HIV infection among 2,400 male and female IDUs. Like other PrEP trials, this study is also examining the effects of taking a daily pill on HIV risk behaviors, adherence to and acceptability of the regimen, and in cases where participants become HIV-infected, the resistance characteristics of the acquired virus. Results are anticipated in late 2012.

Other PrEP Studies

Other trials are underway or planned to examine the safety, adherence, acceptability, and feasibility of other PrEP regimens and dosing strategies. For detailed information on the full range of PrEP trials, visit

Next Steps in Assessing and Maximizing the Benefits of PrEP

PrEP offers a new tool to help combat the HIV epidemic among the hardest-hit populations in the United States and around the world, but its overall impact on the epidemic will depend on many things that at this point remain unknown, including access and acceptability among the populations at highest risk. Impact will also depend upon whether programs implemented in community settings can achieve the key requirements for success, including ensuring regular HIV testing, maintaining high levels of medication adherence, and preventing increases in risk behavior.

CDC and its partners are working to assess many of these key questions to determine how PrEP can most effectively be used in the United States.

  • "Open-label extension" studies of the iPrEx, Partners PrEP, and TDF2 trials -- in which all participants in those trials are provided PrEP knowing that they are taking medication with proven efficacy -- are planned or underway, and will provide additional valuable information in research settings about acceptability, adherence to PrEP, and risk behavior.
  • Demonstration research projects to evaluate PrEP use among MSM are planned in several California cities and Miami to provide similar information in "open-label" studies conducted with new research participants.
  • CDC is working with federal, state, local, and private partners to identify additional ways to evaluate key PrEP implementation questions at community sites providing PrEP as a clinical HIV prevention service.

With limited resources available to combat the HIV epidemic, we will have to carefully consider how to most effectively use this tool in combination with other proven approaches to have the greatest possible impact on the HIV epidemic. Other key strategies such as HIV testing and treatment of individuals with HIV infection are critical, and will need to be expanded to reach the substantial number of Americans who are either unaware of their HIV status or not being effectively treated. CDC estimates indicate that only one-quarter of Americans with HIV currently have their virus suppressed to the levels needed to maintain their own health and prevent transmission to others.

Nevertheless, while expanded HIV treatment for those with HIV infection is essential, it will not be sufficient to end the epidemic. Even if we can improve treatment outcomes for all of those diagnosed with HIV, individuals who do not know they are infected are likely to continue to unknowingly transmit HIV infection to others.

With 2.7 million people becoming infected annually worldwide, including approximately 50,000 in the United States, we must capitalize on every available prevention tool. While the most appropriate uses of PrEP as part of these efforts is yet to be determined, available data suggest that this prevention method, if used strategically and effectively, could be cost-effective and may help reduce the continuing toll of HIV infection in this nation.

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This article was provided by U.S. Centers for Disease Control and Prevention. Visit the CDC's website to find out more about their activities, publications and services.
See Also
More on HIV Medications for HIV Prevention

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