Thursday, May 10, 2012

PrEP: does risk compensation matter?

From today's meeting of the Antiviral Drugs Advisory Committee, which will advise FDA on whether to approve a new prevention indication for Truvada: Susan Buchbinder from the SF Dept of Public Health discusses the potential role of risk compensation in PrEP implementation.  (Risk compensation would occur if patients, perceiving PrEP to reduce their risk of HIV acquisition, start to engage in riskier behaviors and/or reduce their use of other protection methods such as condoms.  Clinical trials on PrEP have not found significant evidence of risk compensation, but can't rule out the possibility in real-world practice.)

Buchbinder notes that in terms of overall risk reduction, even partial PrEP efficacy would offset a fair amount of risk compensation--that is, it would take a lot more unprotected sex to eliminate the benefit of an intervention that reduces risk by, say, 60%.  She also draws an analogy to statins, a partially effective drug intervention used to reduce risk of cardiovascular diseases.  Whereas risk compensation is continually debated in the context of partially effective HIV risk reduction methods such male circumcision and PrEP, she notes, it is rarely discussed in the context of statins: doctors don't withhold statins based on the worry that patients will end up eating more cheeseburgers.

This analogy raises the question of whether the focus on risk compensation in HIV prevention has something to do with social norms: whereas eating an unhealthy diet is common in most groups, are the activities that increase HIV risk--unprotected sex, especially anal sex, and IV drug use--regarded in a way that makes the possibility of their increase seem disproportionately problematic?  Is the concern amplified by cultural taboos? 

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