24/11/08

Prepped for PrEP: are we ahead of ourselves?

When I’m asked: What’s the next big thing in HIV prevention? I usually put Pre-Exposure Prophylaxis somewhere high on the list. We don’t yet know if giving out expensive drugs so that people can have unprotected sex without worrying about HIV will work. But I usually ask people to imagine the headlines in The Daily Mail/ The New York Post if it does.

Now we know. “The £15 pill to protect against HIV” was the headline in Metro, the Daily Mail’s give-away version. More muted than I would expect, but Metro is really the Mail Lite. The article, bylined Jo Steele, does indeed seem to have been stolen wholesale from a much more rigorous piece in the New Scientist, headlined Safer Sex in a Pill.

Missing from the headline is a question mark. While the New Scientist piece does point out that we’re not sure that PrEP works, the Metro piece glosses over the uncertainty, saying (wrongly) that Viread and Truvada “have proven successful in human trials involving 19,000 gay men”. Anthony Fauci is quoted as saying “There’s a lot of buzz about PrEP. There’s some cautious optimism this will work”. I see a lot of optimism, not much of it cautious. My favourite example of the glass being half full comes from Bob Grant, from UCSF. He doesn’t think that people who take a pill so that they can have more unprotected sex will actually have more unprotected sex.

“Bob Grant, who researches HIV prevention at the University of California, San Francisco, and helped run the African trial, speculates that some users may even have less unsafe sex. “PrEP might put people in a different frame of mind,” he says. “When people take a pill a day, that reminds them that they are at risk of catching HIV.”

Hmmm. I took pills every day for about two decades so that I could have unprotected sex without catching pregnancy, and I never once thought: ah yes, I took a pill this morning to help avoid pregnancy, and sex can lead to pregnancy so I’d better not have sex.

I’m all for increasing HIV prevention options, especially ones that have been proven to work (if only in some circumstances, some of the time). But I do think we also have to recognise that what works for an individual may not work so well at a population level — we’ve seen this with the roll-out of ARV among gay men in rich countries. Individually, infectivity goes down, but at the population level, new cases are rising. Look out for a paper and commentary along these lines in The Lancet next week. A number of authors from the WHO will argue that testing all adults annually and putting everyone infected on ARVs would essentially wipe out HIV transmission within 10 years. In a commentary, some other authors from the WHO conclude that it would be a good idea, but might be hard to do in practice.

The truth is that what works in a clinical trial (or even on the much thinner ice of a mathematical model) can not always be made to work in practice. There will be a lot of resistance to PrEP at first, not least from the people who already object to giving out condoms. It’s no bad thing to start thinking now about how to deal with that resistance. (IRMA draws our attention to a Congressional briefing on PrEP on December 4th.) But let’s not get too far ahead of ourselves. There’s no point cashing in political capital in favour of PrEP until we’re sure it works.

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This post was published on 24/11/08 in Science.

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  1. Comment by Roger, 24/11/08, 10:25:

    In the same line look no further than at circumcision, which roll out is currently failing and with it the protective effect at population level.

  2. Comment by Daniel Reeders, 24/11/08, 11:16:

    Great post! I think the PrEP/Pill comparison is a leetle bit unfair though, because pregnancy and HIV/AIDS are not exactly equivalent.

    Something I wanted to mention – MidWest Teen Sex Show is having a funding drive – would it be possible to use the incredible momentum you’ve built around this blog to help them along? A Digg effect for sex and drugs…

  3. Comment by Seth Kalichman, 19/12/08, 10:11:

    Lots of people are getting jazzed about the promise of PrEP. With so many biological approaches to HIV prevention not working, especially our frustration in getting an HIV vaccine, it does seem we are getting ahead of ourselves about PrEP. What especially concerns me is that unlike a vaccine or microbicide, antiretrovirals are readily available and can be misused. Until demonstrated efficacious, taking an unproven pill in place of using a condom will add little to simple wishful thinking. The false promise of not-yet proven means of prevention is attractive. Sort of like the lure of denying that HIV even causes AIDS (for more on AIDS denialism see http://denyingaids.blogspot.com/). Opening up this dialogue can help sort out what we know is true from what we hope is true.

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