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Contemp Clin Trials. 2011 May;32(3):333-8. doi: 10.1016/j.cct.2011.01.005. Epub 2011 Jan 26.

Co-enrollment in multiple HIV prevention trials - experiences from the CAPRISA 004 Tenofovir gel trial.

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Centre for the AIDS Program of Research in South Africa (CAPRISA), Durban, South Africa.



In settings where multiple HIV prevention trials are conducted in close proximity, trial participants may attempt to enroll in more than one trial simultaneously. Co-enrollment impacts on participant's safety and validity of trial results. We describe our experience, remedial action taken, inter-organizational collaboration and lessons learnt following the identification of co-enrolled participants.


Between February and April 2008, we identified 185 of the 398 enrolled participants as ineligible. In violation of the study protocol exclusion criteria, there was simultaneous enrollment in another HIV prevention trial (ineligible co-enrolled, n=135), and enrollment of women who had participated in a microbicide trial within the past 12 months (ineligible not co-enrolled, n=50). Following a complete audit of all enrolled participants, ineligible participants were discontinued via study exit visits from trial follow-up. Custom-designed education program on co-enrollment impacting on participants' safety and validity of the trial results was implemented. Shared electronic database between research units was established to enable verification of each volunteer's trial participation and to prevent future co-enrollments.


Interviews with ineligible enrolled women revealed that high-quality care, financial incentives, altruistic motives, preference for sex with gel, wanting to increase their likelihood of receiving active gel, perceived low risk of discovery and peer pressure are the reasons for their enrollment in the CAPRISA 004 trial.


Instituting education programs based on the reasons reported by women for seeking enrollment in more than one trial and using a shared central database system to identify co-enrollments have effectively prevented further co-enrollments.

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