U.S. Centers for Disease Control and Prevention, “CDC Trial and Another Major Study Find PrEP Can Reduce Risk of HIV Infection among Heterosexuals.” Press Release, July 2011. 1
The practice of giving antiretroviral medications (ARVs) to uninfected individuals to prevent their risk of infection is commonly referred to as preexposure prophylaxis (PrEP). Two recent studies, one conducted by the U.S. Centers for Disease Control and Prevention (CDC) and one by the University of Washington’s International Clinical Research Center (UW), showed that HIV-negative individuals who take a daily dose of certain ARVs commonly used to treat HIV have a significantly reduced risk of contracting the illness. The studies were conducted among heterosexual couples in the African nations of Botswana, Kenya, and Uganda.
- The CDC trial, referred to as TDF2, found that oral PrEP given daily with a tablet containing tenofovir disoproxil fumarate and emtricitabine (TDF/FTC, known by the brand name Truvada®) was found to reduce the risk of HIV infection by roughly 63 percent in the study population. The population for TDF2 consisted of 1,600 sexually active men and women who were not infected with HIV at the beginning of the study.
- The UW study, known as Partners PrEP, showed that individuals at high risk for HIV infection who took a daily tablet containing an HIV medication—either the antiretroviral medication tenofovir or TDF/FTC—were significantly less likely to become infected than those who received a placebo. Partners PrEP enrolled 4,758 HIV serodiscordant couples—those in which only one member is infected with HIV.
A total of 60 million people worldwide have been infected with HIV since the beginning of the pandemic, with an estimated 7,400 new infections occurring daily; PrEP may be a promising weapon in the HIV-prevention arsenal. However, cautions Jonathan Mermin, director of the Division of HIV/AIDS Prevention at the CDC, “It is important that we take time to think how PrEP will be used in the real world . . . PrEP is not for everyone, and it will not solve the epidemic.”2 Both the TDF2 and Partners PrEP trials show that PrEP has tremendous promise as an HIV prevention strategy when other methods are untenable. In addition, TDF2 and Partners PrEP have expanded the populations for which PrEP is proven effective, as both studies exclusively involved heterosexual men and women. Based on previous evidence, the CDC has recommended PrEP solely for men who have sex with menwho are at high risk of contracting HIV in an interim guidance for physicians, but is reviewing the results of both the TDF2 and Partners PrEP trials to determine guidelines for administering PrEP to heterosexual men and women.3 The results of both studies have also exceeded researchers’ expectations. While existing prevention strategies, such as condom use, have been proven effective if used consistently and correctly, those strategies remain out of reach for many people around the globe. For women, in particular, “the current prevention methods are inadequate, since they often do not have the social or economic power to refuse sex or negotiate condom use.”4 Abstinence from sexual activity until marriage has long been promoted as an HIV prevention technique; however, abstinence-only programs have not succeeded in lowering rates of HIV transmission in the United States and there is no evidence to suggest that they fare better in other countries. Both the TDF2 and Partners PrEP trials show that PrEP has tremendous promise as an HIV prevention strategy when other methods are untenable.
1 U.S. Centers for Disease Control and Prevention, “CDC Trial and Another Major Study Find PrEP Can Reduce Risk of HIV Infection among Heterosexuals.” Press Release, 13 July 2011, accessed 5 August 2011, <http://www.cdc.gov/nchhstp/newsroom/PrEPHeterosexuals.html>.
2 David Brown, “Two Studies Show That Drugs Used to Treat AIDS Can Prevent HIV Infection,” Washington Post, 13 July 2011, accessed 5 August 2011, <http://www.washingtonpost.com/national/two-studies-show-that-drugs-used-to-treat-aids-can-be-used-to-prevent-hiv-infection-too/2011/07/12/gIQAN51zBI_story.html>.
3 D. K. Smith et al., “Interim Guidance: Preexposure Prophylaxis for the Prevention of HIV Infection in Men Who Have Sex with Men,” Morbidity and Mortality Weekly Report (Atlanta: Centers for Disease Control and Prevention, 2011), accessed 5 August 2011, <http://www.cdc.gov/mmwr/pdf/wk/mm6003.pdf>.
4 “Partners PrEP Study: Frequently Asked Questions,” University of Washington International Clinical Research Center, 22 February 2011, accessed 5 August 2011, <http://depts.washington.edu/uwicrc/research/studies/files/PrEP_FAQ.pdf>.