With study of injecting drug users, preventive HIV medicine demonstrates protective value to all at high risk

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CDC releases updated Guidance for Pre-Exposure Prophylaxis for the Prevention of HIV Infection: PrEP for Injecting Drug Users, while questions on real-world impact remain

During the Bangkok Tenofovir Study, risk behavior was assessed every three months with an audio-computer-assisted self-interview. Photo courtesy of the Centers for Disease Control and Prevention

During the Bangkok Tenofovir Study, risk behavior was assessed every three months with an audio-computer-assisted self-interview. Photo courtesy of the Centers for Disease Control and Prevention

With a five-year study in Bangkok showing that daily doses of antiretroviral medicine reduced risks of HIV infection among people who inject drugs by at least half, and more with the most consistent use,  antiretroviral medicine as pre-exposure prophylaxis has been shown effective for preventing HIV infection among all groups considered at highest risk for acquiring the virus. In recent years the method of HIV prevention known as PrEP has already been found effective in preventing HIV acquisition in previous studies of men who have sex with men, in HIV-discordant couples, and in sexually active heterosexual men and women. During the same time period, though, two studies of the effectiveness of PrEP for women were ended when the method was found ineffective, ultimately because trial participants were not taking the pills.

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The June 13 CDC Morbidity and Mortality Weekly Report includes the agency’s updated PrEP guidance, as well as this table on previous PrEP studies. Click on image to enlarge

People who use injecting drugs can be exposed to HIV through shared syringes, as well as through sexual contact and have been highly impacted by HIV, while funding policies and laws have kept supplies of new sterile syringes out of reach for most. In some regions of Eastern Europe and Central Asia, according to the Centers for Disease Control and Prevention, injecting drug use accounts for as much as 80 percent of HIV incidence. On Wednesday, the CDC, which supported the trial, and which in 2012 issued guidance on the use of PrEP to prevent HIV acquisition among sexually active heterosexual men and women and men who have sex with men, updated its recommendations to include prevention among injecting drug users. The recommendations are included in today’s Morbidity and Mortality Weekly Report, and the study was published online today in The Lancet.

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Bangkok Tenofovir Study participants were given a choice of daily directly observed treatment or monthly visits.

The Bangkok Tenofovir Study followed more than 2400 patients at 17 drug treatment clinics from 2005 to 2010, randomly assigning the trial volunteers to placebo or tenofovir groups, but giving them the choice of taking the pills on their own, or under direct observation. Those who were directly observed and took the pills most consistently, researchers discovered, showed a 74 percent reduced risk of HIV acquisition.

Advocates of HIV prevention research say with the Bangkok study results confirming that PrEP is a viable means of reducing HIV acquisition risk,it should be added to other proven methods and made available to those whose circumstances put them at the greatest risk.

“We know that this is a truly effective intervention,” Mitchell Warren, AVAC executive director said Wednesday. “We now need to know what happens next.”

He noted that two and a half years have passed since the first study results indicating the effectiveness of PrEP. The latest results, he said, should add impetus to efforts to meet the needs of a neglected population and not supplant other proven interventions. “Comprehensive harm reduction, along with human rights protections, are the fundamental HIV prevention tools for injecting drug users,” Warren said. “We know syringe exchange works, we’ve known it for years.”

Making PrEP available to those who need it most will offer an opportunity to discover and address issues that have interfered with consistent use in previous studies. “That’s a new conversation we’re just beginning to be able to have,” Warren said. “Within the next year, a comprehensive package of demonstration projects should be planned, funded and launched in countries around the world.”

PrEP could be a particularly effective intervention for injecting drug users, Veronica Miller, Executive Director of the Forum for Collaborative Research said Wednesday. While previous studies of PrEP among diverse populations have been more controlled than the conditions of actual PrEP rollout would be, the Bangkok study worked in settings similar to those in which future PrEP program enrollees would be found — drug treatment clinics as well as correctional institutions, Miller said. “It’s a contained setting with medical supervision.” In addition, she said, the use of PrEP among a population being treated for drug addiction offers the possibility that the method could be “a targeted, specific short term intervention,” which would add to protections offered during treatment.

At the same time, while the Bangkok study was the first to examine the effectiveness of PrEP in a population among whom HIV is transmitted through syringes, the study does not conclusively show that PrEP prevents that means of transmission, Salim Abdool Karim, of the Center for the AIDS Programme of Research in South Africa cautioned in a comment accompanying the Lancet publication of the study results. Determining with certainty if an HIV infection was transmitted by a shared needle or through sex is not possible, he explains in the comment. “As a result, PrEP is not a replacement for politically sensitive needle exchange programmes,” to prevent transmission through shared needles, he writes. Still, he concludes, included with other efforts, PrEP “could make a useful contribution to the quest for an AIDS-free generation.”

AVAC and the Harm Reduction Coalition will host a global advocates teleconference to discuss the Bangkok Tenofovir Study, with trial investigators and others 10 a.m. Tuesday, June 18. The registration link is here.

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