Infectivology Xagena

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HIV prevention: sexual behaviour of heterosexual men and women receiving antiretroviral pre-exposure prophylaxis

Scarce data are available to assess sexual behaviour of individuals using antiretroviral pre-exposure prophylaxis for HIV prevention. Increased sexual risk taking by individuals using effective HIV prevention strategies, like pre-exposure prophylaxis, could offset the benefits of HIV prevention.
Investigators have studied whether the use of pre-exposure prophylaxis in HIV-uninfected men and women in HIV-serodiscordant couples was associated with increased sexual risk behaviour.

Researchers undertook a longitudinal analysis of data from the Partners PrEP Study, a double-blind, randomised, placebo-controlled trial of daily oral pre-exposure prophylaxis among HIV-uninfected partners of heterosexual HIV-serodiscordant couples ( n=3163, greater than or equal to 18 years of age ).

Efficacy for HIV prevention was publicly reported in July 2011, and participants continued monthly follow-up thereafter.

Investigators used regression analyses to compare the frequency of sex-unprotected by a condom during the 12 months after compared with the 12 months before July 2011, to assess whether knowledge of pre-exposure prophylaxis efficacy for HIV prevention caused increased sexual risk behaviour.

Researchers analysed 56 132 person-months from 3024 HIV-uninfected individuals ( 64% male ). The average frequency of unprotected sex with the HIV-infected study partner was 59 per 100 person-months before unmasking versus 53 after unmasking; no immediate change ( p=0.66 ) or change over time ( p=0.25 ) after July 2011, was recorded.

A significant increase in unprotected sex with outside partners after July 2011, was identified, but the effect was small ( average of 6.8 unprotected sex acts per year vs 6.2 acts in a predicted counterfactual scenario had patients remained masked, p=0.04 ). Compared with before July 2011, it was noted no significant increase in incident sexually transmitted infections or pregnancy after July 2011.

The study has shown that pre-exposure prophylaxis, provided as part of a comprehensive prevention package, might not result in substantial changes in risk-taking sexual behaviour by heterosexual couples. ( Xagena )

Mugwanya KK et al, The Lancet Infectious Diseases 2013; 13: 1021-1028