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.

Sunday, October 24, 2010

Never Mind Efficacy, Think of the Profits

There's an interesting article in the Emerging Health Threats Forum about bird flu behavior change campaigns and people's perception of risk. It was found that "People who witness avian flu outbreaks in animals near them fear the disease less than those with no experience of it".

Most HIV prevention campaigns have attempted to influence people's sexual behavior by warning them about certain risks and telling them how to avoid them. Some of these campaigns have been assessed and the results tend to show that many people continue with the behaviors considered to be risky.

Speculation has suggested that HIV transmission rates in Uganda, and eventually in some other countries, started to decline once people realized that many of those around them were becoming sick and dying. This is unlikely to be true because high death rates would have occurred some years after declines in transmission started.

However, much HIV prevention work continues with the assumption that people will modify risky behavior once they know that it is risky and what steps they can take to ensure that they don't become infected. And perhaps the assumption is, to some extent useful. Perhaps people will eventually begin to take precautions and the bulk of sexual transmission of HIV will be eradicated.

Wide availability of PrEP in high HIV prevalence countries may become a 'protective' behavior, something people who cannot avoid sexual risks can take to reduce the risk of infection. In textbook cases, where HIV transmission really does occur because people are taking unnecessary and avoidable sexual risks, PrEP may even have a substantial effect on sexual transmission.

Unfortunately, a good deal of sexual transmission is probably not of the textbook variety. The incredibly high rates of risky sexual behavior attributed to Africans in the textbooks are more likely to be a widely shared fantasy, stubbornly held by those who are in the best position to see how such views are completely without foundation.

But even where PrEP is available to prevent some sexual HIV transmission, it is unlikely to have any impact on non-sexual HIV transmission. The fact that UNAIDS and other institutions are not even targeting non-sexual transmission doesn't help, but giving out pills, to however many people, is not the most expeditious means of reducing, for example, health care related exposure to HIV.

It is not a new discovery that behavior and behavior change are complicated and difficult to effect. And this is not to say that some kinds of behavior change shouldn't be attempted and facilitated. However, concentrating all our attention on sexual HIV transmission, without even attempting to find out how much of the virus is spread though non-sexual modes, results in an unknown level of avoidable infection.

PrEP may hold some promise for certain kinds of sexually transmitted HIV but it will not eradicate the virus. And it will have little or no impact on non-sexual transmission, which is probably responsible for a large proportion of the highest prevalence epidemics, all of which are found in a handful of sub-Saharan African countries.

Some advocates of PrEP may truly believe that it could eventually play a part, perhaps a big part, in eradicating the virus. People who believe this don't know very much about HIV. But I suspect that PrEP is just a clever way of increasing HIV drug sales by several hundred percent, perhaps even several thousand percent.

Having a ready supply of trial participants in countries where the virus is common will help a lot in getting the drugs on the market. Meanwhile, epidemics in African countries continue on trajectories that are completely independent of any HIV prevention programs that have taken place so far.


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