A tale of two trials: how adherence is everything in PrEP  Gus
Cairns Published: 06 March 2012 Jared Baeten. Photo by Gus
Cairns / aidsmap.com  Adherence makes all the difference to the
efficacy of pre-exposure prophylaxis (PrEP), the 19th Conference
on Retroviruses and Opportunistic Infections (CROI) heard today.
In April 2011, the FEM-PrEP study found that giving HIV-negative
women tenofovir/FTC (Truvada) pills to prevent their acquiring
HIV was totally ineffective: there was no difference in HIV
incidence between women taking Truvada and women taking placebo.
In July 2011, however, the Partners PrEP study found that
Truvada was 73% effective in preventing HIV transmission between
heterosexual partners of different HIV status.  How do we
explain why giving HIV-negative women antiretroviral pills made
no difference to the HIV infection rate in one trial, but
prevented at least two in every three infections in the other?
The difference, it appears, is that in the Partners PrEP trial,
adherence to the study