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.

Saturday, October 20, 2012

Give ARVs To Those Who Need Them; PrEP Can Wait


It's been a while since I've written anything about PrEP and it's hard to keep up with two blogs. But there have been a few articles on the subject. One, and I've only seen the abstract, finds that PrEP has high acceptability but that adherence and use are more challenging. This may be a reflection of the sheer idiocy of throwing drugs at a disease that is treated in almost complete isolation from all other diseases, from the conditions in which people live, from their overall health status, etc.

Interestingly, people on PrEP ran the risk of being perceived as HIV positive, giving rise to stigma, rumors and relationship difficulties. A paper about lymphatic filariasis reports that people have difficulty understanding why they should take pills for a condition for which they have no symptoms, and also why they should take the same pills for what they see as two different conditions (swollen legs and swollen testicles).

The authors of the PrEP article note that "adherence was challenged by complexities of daily life, in particular post-coital dosing adherence suffered from alcohol use around time of sex, mobile populations, and transactional sex work". The research into giving antiretroviral drugs to HIV negative people took place in Kenya, a country where many HIV positive people with a critical need for the drugs are not receiving them, and where many babies are still being infected by their mothers (or perhaps through some other route that antiretroviral drugs will not be able to address, such as through unsafe healthcare).

A review of a mathematical modelling study of PrEP mentions the ethical problems of rolling out such a program in a country where many HIV positive people are not yet on antiretrovirals. The article finds that the strategy would be cost effective in a middle income country, such as Peru, but only if it was highly targeted. However, this is where PrEP and most other HIV interventions come unstuck in African countries. HIV in high prevalence African countries is characterized by not disproportionately affecting just a few easily identifiable groups. While prevalence is high in certain groups, the largest groups of HIV positive people don't have obvious sexual risks that could easily be targeted. Also, these groups are far too large for any African country to afford.

What I don't really understand about PrEP though, is why it is necessary at all. Proponents of the use of antiretroviral drugs in as many scenarios as possible (early treatment, lifetime treatment for women receiving prevention of mother to child treatment, etc) tell us that someone on ARVs is not very infectious. If PrEP could be targeted at people who are thought to be at risk, targeting those who put them at risk would seem like a much better prospect; that is, targeting people who are already HIV positive. They are a far smaller group, for a start, and this would be a good reason for putting all HIV positive people on ARVs as soon as they have a clear clinical need for them.

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