PEP, PrEP, or even PeEP?
I finally got around to reading the paper in the New England Journal on the use of daily antiretroviral therapy for the prevention of HIV infection (full text here). In hospital epidemiology we're very familiar with post-exposure prophylaxis (PEP) for healthcare workers who sustain percutaneous exposures or blood/body fluid exposures to mucous membranes. This paper evaluated pre-exposure prophylaxis (PrEP) for men who have sex with men by having the study subjects take a daily dose of truvada. New HIV infections were compared in the treatment group to men who were assigned to take a placebo daily. There were roughly 1200 men in each study arm. On average the men were in their late 20s, had more than 1 sex partner weekly, about 60% reported unprotected anal intercourse, and they were followed for roughly 1 year. There were 36 new HIV infections in the Truvada group (2.9%) and 64 new infections in the placebo group (5.3%). This represents a 44% relative risk reduction. Sounds pretty good, but that translates to only a 2.4% absolute risk reduction (the infection rate in the treated group subtracted from the infection rate in the placebo group). When the subset of men with detectable drugs levels (i.e., those who were compliant with Truvada) were compared to those without detectable drug levels, the relative risk reduction was 92%. "That's huge," exclaimed Dr. Anthony Fauci, the head of the National Institutes of Allergy and Infectious Diseases, in the New York Times.
So here we have an intervention that appears to be efficacious but not effective (that is, it works when you take the drug, but in the real world many people just won't take it--we've talked about this before). By my calculations, compliance appeared to be about 38% in the study. However, I think we can be sure that compliance would have been even less in the real world if the study subjects had to pay for the Truvada at the retail price of $13,000 yearly. We're also not told whether those who took the drug faithfully may have also been highly compliant with condom use, which may make the drug appear to be more effective than it actually is. So, in the end, I don't think that the impact of this study will be huge. In fact, I doubt it will have much impact at all. The real issue, it seems to me, is helping people to reduce risk the old fashioned way (fewer sexual partners and consistent use of condoms), until the day finally arrives when we have an effective vaccine for HIV.
Switching gears, as a hospital epidemiologist, I wondered if there is a role for PrEP in the hospital. Let's consider the case of a an untreated HIV infected patient with a high viral load who needs cardiac or orthopedic surgery soon. Should the operative team be given PrEP or perhaps peri-exposure prophylaxis (PeEP), with dosing the day before, the day of the procedure, and the day after? If I were the surgeon, I would be interested in that.
So here we have an intervention that appears to be efficacious but not effective (that is, it works when you take the drug, but in the real world many people just won't take it--we've talked about this before). By my calculations, compliance appeared to be about 38% in the study. However, I think we can be sure that compliance would have been even less in the real world if the study subjects had to pay for the Truvada at the retail price of $13,000 yearly. We're also not told whether those who took the drug faithfully may have also been highly compliant with condom use, which may make the drug appear to be more effective than it actually is. So, in the end, I don't think that the impact of this study will be huge. In fact, I doubt it will have much impact at all. The real issue, it seems to me, is helping people to reduce risk the old fashioned way (fewer sexual partners and consistent use of condoms), until the day finally arrives when we have an effective vaccine for HIV.
Switching gears, as a hospital epidemiologist, I wondered if there is a role for PrEP in the hospital. Let's consider the case of a an untreated HIV infected patient with a high viral load who needs cardiac or orthopedic surgery soon. Should the operative team be given PrEP or perhaps peri-exposure prophylaxis (PeEP), with dosing the day before, the day of the procedure, and the day after? If I were the surgeon, I would be interested in that.
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