PrEP Could Prevent About Three Million HIV Cases in Sub-Saharan Africa Over 10 Years, Study Says
Pre-exposure prophylaxis -- the practice of HIV-negative people taking antiretroviral drugs before potential exposure to the virus -- could prevent as many as three million new HIV cases over 10 years in sub-Saharan Africa, according to a study published online Wednesday in PLoS One, Reuters reports (Fox, Reuters, 9/18).
For the study, researchers at the University of Pittsburgh School of Medicine and Imperial College London used a computer model to predict by how much Gilead Sciences' antiretroviral tenofovir, sold under the brand-name Viread, could reduce new HIV cases. In studies involving monkeys, tenofovir has been shown to be effective in preventing transmission of the simian version of HIV, AFP/Yahoo! News reports (AFP/Yahoo! News, 9/18). According to Reuters, the model simulated an African country where 20% of the adult population is living with HIV/AIDS (Reuters, 9/18).
The researchers found that if the drug was effective 90% of the time and was given daily to 75% of sexually active people ages 15 to 49, it could reduce HIV cases by 74% over 10 years (AFP/Yahoo! News, 9/18). The researchers estimated that such a program would cost about $2 billion over 10 years in Southern Africa (Reuters, 9/18). If the drug was effective 60% of the time and was taken by 50% of sexually active people ages 15 to 49, it would reduce HIV cases by about 25% over 10 years, according to the researchers. In addition, if the drug was effective 30% of the time and used by 25% of sexually active people, it would reduce new cases by 3.3% over 10 years, the study found (AFP/Yahoo! News, 9/18).
According to the study, about 2.7 million to 3.2 million new HIV-1 cases could be prevented over 10 years in sub-Saharan Africa by providing PrEP to populations with high sexual activity. John Mellors, a professor at the School of Medicine who helped direct the study, added that PrEP programs should include counseling to determine who should take the treatment and ensure that people do not have a false sense of invulnerability to HIV. "If the public feels that they can take a pill and now have more sex, the effect of the PrEP will go way down," Mellors said.
According to Mellors, the researchers looked at the efficacy of PrEP, how quickly the target population begins therapy and whether they continue therapy, and what population should be targeted. Mellors said that providing PrEP to the two groups at highest risk for HIV, or about 18% of the population, would be the most cost-effective approach (Reuters, 9/18). Ume Abbas, an assistant professor at the School of Medicine and lead study author, added that even if PrEP with tenofovir is found to be effective in humans, it is "never going to be feasible to treat the entire population."
U.S. health authorities are conducting additional studies on PrEP with tenofovir to determine its effectiveness among high-risk groups, such as commercial sex workers, injection drug users and men who have sex with men. The earliest results will not be available until at least early 2008, AFP/Yahoo! News reports (AFP/Yahoo! News, 9/18). CDC has enrolled injection drug users in Thailand and high-risk heterosexual men and women in Botswana for safety and efficacy trials, and the agency is conducting a safety trial of tenofovir among MSM in the U.S., according to a CDC fact sheet. In addition, NIH is conducting a PrEP safety and efficacy trial among MSM in Peru and Ecuador (CDC fact sheet, April 2007).
The study is available online.