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, November 2, 2010

Why do Microbicide Trials Make No Effort to Establish Mode of Transmission?

In contrast to the CAPRISA vaginal microbicide trial, which received copious amounts of coverage, not so much is said about the PRO2000 gel trial. The latter trial was deemed safe but it did not prevent transmission of HIV to women.

As is customary in these trials, no attempt was made to establish how HIV was transmitted. It was just assumed that it was sexually transmitted and male partners were not tested.

Incidence was high, between 3.9 and 4.7 per 100 woman years, despite condom use being high. Condom manufacturers might even be a little bit curious as to why people who were not engaging in sex very much, were avoiding unsafe sex and had been selected because they were HIV negative, seemed to be so susceptible to HIV infection. They were even screened for other sexually transmitted infections (gonorrhea and chamydia).

The ostensible aim of microbicide trials will not have been achieved. In order to prevent HIV transmission it needs to be clear how the virus is being transmitted. Microbicides may have some influence on non-sexual HIV transmission but people are unlikely to use them to prevent infection when they are not having sex unless they are made aware of the existence of such risks.

And even then, people will not be choosing to use vaginal microbicides. They would not be the first choice if you were a man, going for an operation, visiting the hairdresser, injecting drugs, pregnant or about to give birth, getting a tattoo, etc.

The failure to establish mode of transmission is not just a flaw. Non-sexual modes of transmission may turn out to be responsible for a significant number of HIV infections in some epidemics, such as those in high-prevalence sub-Saharan African countries.

If so, vaginal gels may achieve little more than continuing to deflect attention from the abysmal health services that are undoubtedly infecting African patients with all manner of diseases, not just HIV.


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