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Safer sex...

Posted by guscairns on 11 Oct 2012 at 14:02 GMT

These findings suggest that under some circumstances, PrEP could be a cost-effective tool to reduce new HIV infections. However, as the researchers discuss, PrEP is expensive and only partly effective. Moreover, its effectiveness depends on two behavioral factors—adherence to a strict drug regimen and continued practicing of safe sex—both of which remain hard to predict.

Just one comment: This study certainly shows that adherence to a strict drug regimen is likely to be crucial to the impact of PrEP, but interestingly, it does not find that continued practicing of safe sex is crucial, or only to a surprisingly limited extent. Under the low-coverage, highly-targeted scenario, PrEP would remain cost effective if condom use fell by 30% and probably cost effective if it halved; and, as the authors say, the adoption of PrEP would only lead to an increase in HIV incidence if condom use was abandoned and PrEP was only 44% efficacious. Although we hope risk behaviour will not rise, not least because it will cause other STI-related morbidity, it is not the most or second-most important limiting factor on the likely effectiveness of PrEP.

No competing interests declared.