Men who have sex with men are at higher risk for HIV in part because the virus is more easily transmitted during anal sex, but also because in many parts of the world, the stigma against homosexuality is so high that gay men and women often don’t receive the same access to health care as their straight counterparts. Marrazzo hopes that the WHO’s guidelines, published in anticipation of next week’s International AIDS Conference in Melbourne, Australia, will help reduce that stigma by acknowledging the health care needs of this HIV-vulnerable population.

Will they take it?

Marrazzo also points out that despite research showing how effective the drugs can be, even participants in HIV prevention studies don’t take their medication daily, or sometimes, even at all. She led a similar study testing Truvada or an antiretroviral vaginal gel in women in Africa and found that the drugs were not effective because so few of the women took them regularly. Adherence in the iPrEx study and some other studies of daily HIV prevention medicine was high enough to show the pills’ power to block infection, but still far from 100 percent.

“Just because the drug is approved, doesn’t mean it will be prescribed. Just because people fill their prescriptions doesn’t mean they will take it, and just because they take it doesn’t mean they will take it regularly and correctly,” Marrazzo said.

Fred Hutch researchers are working on approaches to combat problems with daily dose adherence. The HIV Prevention Trials Network is planning trials of an injectable antiretroviral drug that may only need to be taken every four months. The Microbicide Trials Network is now conducting a clinical trial in several African countries testing a vaginal ring containing preventive drugs that only needs to be replaced every month.

“That takes away some of the user challenges,” said Dr. Jennifer Balkus, an HIV researcher at Fred Hutch who is helping conduct the vaginal ring trial.

Not a magic bullet

Although skipping too many doses of the drug will decrease its effectiveness, the iPrEx study found that even four doses per week reduced infection risk by 96 percent. Marrazzo is concerned about those who take the pill even less frequently but still falsely believe they are protected from HIV infection and thus practice riskier behavior than they would if they weren’t taking the pill.

But other than user error, the pill is very safe. Those starting the drug may have initial mild stomach upset but tend to habituate quickly, Marrazzo said. And despite the fact that the drugs in Truvada are the same used to treat HIV, studies have found that drug resistance from inconsistent use is rare. Of people who skipped doses of the drug and became HIV infected, the vast majority still responded to antiretroviral treatment.

HIV prevention researchers caution that PrEP should not be viewed as an alternative to condoms. Marrazzo points out that syphilis is on the rise among gay men in many regions, including Seattle.

“[Truvada] is not a magic pill,” she said. “It’s a magic pill to prevent HIV, but it’s not a magic pill to keep yourself sexually healthy.”

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