On the effectiveness of PrEP in preventing HIV infection and what this might mean
I first heard of pre-exposure prophylaxis drug treatments for HIV in December of 2005, when I came across a widely-syndicated article talking about the off-label use of tenofovir by sexually active gay men to ward off infection.
“Taking a T.” That’s what HIV-negative gay men call the growing practice of downing the AIDS drug tenofovir and, with fingers crossed, hoping it protects them from the virus during unprotected sex.
It’s being sold in packets along with Viagra and Ecstasy in gay dance clubs — and even prescribed by physicians, say doctors and AIDS prevention experts. The trend has alarmed public health officials. There is no proof that tenofovir protects against HIV transmission, they say. People who practice unsafe sex while taking the drug could still become infected or suffer side effects from it.
Recreational use of AIDS drugs also might increase overall resistance to the medications, HIV experts say. “This is a very worrisome development,” said Dr. David Hardy, an HIV doctor at Cedars-Sinai Medical Center in Los Angeles. He said the drug could lead to an even further erosion of condom use, which studies show has been falling among high-risk populations.
A survey released in July by the U.S. Centers for Disease Control and Prevention, conducted at gay pride events in four cities, found that 7% of uninfected men had taken an AIDS medication before engaging in risky behavior and that about a fifth had heard of someone who had.
[. . .]
“If we find out this works, even in some people, we would never recommend people stop using condoms or reduce their number of sexual partners,” said Jeff Klausner, STD prevention director for the San Francisco Department of Public Health. Nonetheless, there is some research that suggests taking the drug prophylactically can reduce the risk of transmission. Based on promising earlier research, the CDC is funding two clinical trials, begun last year in Atlanta and San Francisco, on whether tenofovir, a staple of the current HIV drug regimen, may act as a shield to infection — much like how a birth control pill can help prevent pregnancy. Each trial is giving 200 high-risk men a daily dose of tenofovir and monitoring them for two years.
The idea struck me, and my commenters, as somewhat ludicrous. Why abandon condoms—a technology that has been proven to be very effective in preventing HIV infection—in favour of a drug that might inhibit HIV infection? (That the article described how some gay users combined their tenofovir usage with ecstasy and other party drugs didn’t make the idea sound much brighter.)
Even so, from these apparently unpromising beginnings tenofovir has lived up to its promise. When combined with emtricitabine as Truvada, the result is a drug that when taken consistently, does a superb job of preventing the sexual transmission of HIV between couples, whether same-sex or opposite sex. Pre-exposure prophylaxis for HIV works. Combined with treatments for HIV that reduce viral load to undetectable levels and prevent further transmission of the virus, it’s starting to look very much as if the HIV pandemic among gay/bisexual men is eminently controllable through drugs. As Josh Barro notes in The New York Times, only a few groups like the AIDS Health Foundation of Los Angeles criticize PrEP, arguing that it might lead people to abandon condom usage altogether and paradoxically worsen affairs.
A.H.F. warns against widespread PrEP use on two grounds: In clinical trials, many subjects did not take Truvada nearly as often as prescribed, leaving themselves vulnerable to infection; and even though C.D.C. guidelines call for PrEP patients to use condoms, widespread reliance on the drug could discourage condom use, leading to an increase in H.I.V. and other sexually transmitted infections. In the ads running this week, the foundation warns that “the C.D.C.’s ill-advised strategy of mass treatment with Truvada poses a significant risk to the condom culture, which while it has eroded, has still prevailed among gay men for three decades.”
These sorts of concerns are frequently voiced by prominent gay men; last week, the actor Zachary Quinto wrote for The Huffington Post that he has “heard too many stories of young people taking PrEP as an insurance policy against their tendency toward unprotected non-monogamous sex.” But the consensus among public health experts is the opposite: PrEP’s effectiveness in preventing transmission outweighs the risk that people won’t take their pills, or will stop using condoms.
“I find the adherence is much better in real life, especially for PrEP, than in studies,” said Dr. Ray Martins, the medical director at the Whitman-Walker clinic in Washington, D.C., where approximately 170 patients are on PrEP. He said no PrEP patients at Whitman-Walker had contracted H.I.V. since the clinic started prescribing it two years ago. The iPrEx study, which led to PrEP’s approval by the F.D.A. in 2012, was a global one, and adherence was much higher in the United States than overall, especially in San Francisco, where 90 percent of tests of participants’ blood found detectable levels of Truvada eight weeks after it was prescribed.
As for driving people away from condoms, the iPrEx researchers have found that giving people Truvada has not led to riskier behaviors. That’s surprising, but it’s explained in part by the fact that baseline condom use among gay men is already often poor, PrEP or no PrEP.
Evan J. Peterson’s essay in The Stranger, “The Case for PrEP, or How I Learned to Stop Worrying and Love HIV-Positive Guys”, draws from his personal experience and that of his peers to suggest that PReP simply provides extra safety. I could get behind that.
The only problem? Cost. Here in Canada, Québec is the only province to have PrEP guidelines for Truvada; Québec also has a drug plan that soaks up most of the enormous costs associated with the PReP regimen. I do not have a thousand or so extra dollars a month here in Ontario to pay for this prescription myself, and I suspect that most other Ontarians would be in something like my current position. Until something happens—the cost comes down, perhaps, or some sort of government drug plan gets introduced—Truvada for PReP will be something I just won’t be able to access.
I could, if I wanted, imagine a grim sort of scenario where the sexual marketplace shifted in uncomfortable directions as condom usage dropped in response to PrEP while PrEP itself remained inaccessible to many or most people involved. I’d prefer not to imagine this: I’d like to think modern medicine can save us all, properly incentivized. I suppose we’ll have to wait and see what happens next.
