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.

Monday, November 22, 2010

Will People Use Condoms With Pre-Exposure Prophylaxis or Microbicides?

A trial of combined condom and diaphragm use found that, although condom use increased during the trial, it returned to pre-trial rates afterwards. A commentator notes "What happens after trials has always remained very much a mystery". This appears to be true, and it's very disturbing.

Trial conditions are very different from non-trial conditions. Strict protocols are observed, at least in theory, so one would expect behavior to be substantially different once the intervention in question moves into the field. Especially when the trials show that the intervention only produced a small or temporary change in behavior. But results may even be a mere artefact.

Results of trials of mass male circumcision, microbicides (such as the tenofovir based gel tested in the CAPRISA trial), pre-exposure prophylaxis, test and treat strategies and other approaches to HIV prevention, which depend on the possibility of influencing sexual behavior, all share the risk of being artefacts.

Ariane van der Straten was involved in the Methods for Improving Reproductive Health in Africa project. This showed that, in many areas, the interventions involving diaphragms and lubricant, in addition to condoms and counselling employed for the control group, resulted in slightly higher rates of HIV transmission. However, the differences were not statistically significant.

Van der Straten points out that "it is a challenge to use concurrent HIV prevention methods, particularly barrier methods". All the technical solutions mentioned above require people to continue using condoms, even after circumcision and/or using microbicides or taking pre-exposure prophylaxis. Does she mean 'it is a challenge' or 'it is probably inadvisable'?

The study emphasised an unmet need for birth control, but this is hardly a surprise.

Van der Straten's concluding remark is particularly related to one of the assumptions about microbicides, though it may apply equally to pre-exposure prophylaxis. That is the claim that they are 'female-controlled'. Van der Straten says "In the past we have been naive, thinking that female-controlled methods could be used independent of men's involvement, but it's difficult to use any of these methods secretly, so there is a need to involve male partners in female-controlled methods so that they support their partners".

The full report is also freely available online.


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