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.

Tuesday, August 9, 2011

Vital Distinction Between Absolute and Relative Risk Reduction

In order to understand how misleading all the jubilation about recent PrEP trials is, have a look at one of Joseph Sonnabend's two blogs. He explains the difference between relative risk reduction, which is the widely reported finding from the trials, and absolute risk reduction, which is the very low figure that doesn't seem to have been reported at all.

The first blog launches straight into explanations of the two risk figures and an account of why the difference matters so much. But either blog will demonstrate how the whole PrEP issue has been blown up into a 'game changer', in the words of the HIV industry.

Sonnabend shows that the absolute risk reduction is only 2.3%, a far cry from the 44% relative risk reduction reported, which doesn't really give you any way of evaluating the trial results. He also points out that 45 people need to be treated with Truvada to prevent one HIV infection.

There are over 40 million people in Tanzania and only a few hundred thousand of them currently receive antiretroviral drugs, out of well over one million HIV positive people. If PrEP just involved drugs it might be possible to work out the exorbitant amounts of money required, but drugs are only part of it.

It's time for a bit of honesty in reporting figures when it comes to drug trials. There are millions of HIV positive people and tens of millions of people who may be at risk. They deserve the truth.


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