Pre-Exposure Prophylaxis or PrEP

Pre-exposure prophylaxis (PrEP) involves putting HIV negative people on antiretroviral drugs (ARV) with the aim of protecting them from HIV infection. This blog looks at some of the pros and cons of PrEP.

Wednesday, April 13, 2011

PrEP Should Never Be First Line of Defence Against HIV

There's an interesting exchange that I heard about through JournalWatch. Readers of HIV/AIDS Clinical Care journal were asked if they would prescribe PrEP for a high-risk patient. Remarkably, 45% said they would not. More surprisingly, 35% said they would prescribe PrEP intermittently, surprising because this is not a currently recommended use. Only 20% said they would prescribe daily PrEP, the only use that is  currently available.

But two detailed responses outline what the practitioner would do, step by step. And it is these steps that makes me wonder what form PrEP prescription would take in developing countries, where most people are unlikely ever to see a doctor.

Those with only vague notions of what PrEP is, anyone who has been informed by following the mainstream press, might think it is a pill that you can take to prevent yourself from being infected with HIV. In fact, it's a pill that may play some small part in reducing the probability of infection if you also take other precautions, such as always wearing a condom, reducing your number of partners, etc.

As one of the practitioners says, PrEP "should never be the first line of defense against HIV infection". The same practitioner says "the healthcare system [in the US] currently lacks the infrastructure to support PrEP care in the manner recommended by the CDC". Whatever Western health infrastructures lack, they sure as hell will not be found in developing countries.

But there is a sort of paradox about behavioral interventions that aim to reduce HIV transmission: PrEP depends on strict adherence, which is a behavioral matter. Whether someone is considered to be at high or low risk of HIV infection is based on their behavior. If their behavior is tractable, their risk can be reduced. If their behavior is not tractable, their risk can not be reduced.

So, if someone is the sort of person who would adhere strictly to a PrEP prescription, they would be likely to benefit from PrEP. But then they would be unlikely to be at high risk of infection. But then a person would be unlikely to be able to benefit from PrEP if they are genuinely at high risk of infection because of their behavior.

Perhaps a partner of someone whose sexual behavior puts them at high risk of HIV infection could benefit. They would need to take other precautions aside from PrEP, otherwise it is unlikely to give them much protection. But penile-vaginal sex is not particularly high risk, so PrEP is unlikely to be the intervention of choice anyway.


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