Willingness to Participate and Enroll in a Phase 3 Preventive HIV-1 Vaccine Trial

Characterizing high-risk populations who are willing to participate (WTP) in HIV vaccine trials is important for assessing the feasibility of large-scale efficacy trials. This study examined WTP in an HIV vaccine trial among participants in an ongoing prospective study of HIV incidence and risk behaviors among young gay and bisexual men in Vancouver, British Columbia, Canada. The authors identified independent predictors of being WTP in an HIV vaccine trial and considered the implications of these findings for the design and implementation of phase 3 trials. In addition, they examined self-reported reasons for not participating in an ongoing phase 3 vaccine trial. In a subanalysis, the authors assessed changing WTP in HIV vaccine trials from 1997 to 2001.

Since May 1995, young gay and bisexual men have been recruited into the study through outreach at gay community events, community health clinics or local physicians' offices, where they complete a confidential self-administered questionnaire and provide a blood sample for HIV testing. Men are eligible to participate if they are between 15 and 30 years of age, live in the greater Vancouver region, and have not previously tested HIV-positive. Follow-up visits are conducted annually.

Participants were provided with pre- and post-test HIV counseling by trained personnel at every visit. Information was collected on sociodemographic characteristics, sexual behaviors with men, and psychosocial variables.

Self-reported participation in the ongoing phase 3 AIDSVAX B/B trial and reason for not participating in this vaccine trial were collected from seven specific questions included in the Vanguard Project questionnaire since 1999. The AIDSVAX B/B trial is an international, double-blind, placebo-controlled study of the rgp120/HIV-1 vaccine. In this trial, subjects are randomized in a 2:1 ratio to receive either vaccine or placebo at months 0, 1, 6, 12, 18, 24, and 30. Participants were excluded if they had not engaged in anal intercourse with a male partner at least once in the previous year or if they were in monogamous relationships with the same seronegative male partner over the same time period. The Vanguard Project did not actively recruit participants into the AIDSVAX B/B trial; however, the participants were informed of the trial and educated about basic trial concepts using mailings, e-mails, and newsletters collected at the same time as questionnaires.

A total of 474 Vanguard Project participants completed a questionnaire between October 1999 and May 2001. Eligible participants included 214 who were WTP and 97 who were not WTP. The 129 participants who were unsure of their WTP were considered separately. Participants ineligible for this study included 13 respondents who were HIV-positive and 21 who were already participating in the AIDSVAX B/B trial in Vancouver.

Gay and bisexual men who expressed WTP in an HIV vaccine trial were more likely to be socioeconomically disadvantaged and sexually risky and to have a high-perceived risk of HIV infection. Reasons for not enrolling in the AIDSVAX B/B phase 3 trial in Vancouver included fear of infection, serious health problems, and being denied health insurance or having missed the deadline for enrollment. Comparing WTP in 1997 in the context of a hypothetical trial with WTP in 2001 in the context of the ongoing AIDSVAX B/B phase 3 trial, there is evidence of a decline in interest in vaccine trial participation since 1997.

The authors suspect that self-reported willingness to enroll in 1997 did not translate into actual enrollment into the AIDSVAX B/B trial as measured in 2001, because of lack of complete or appropriate information on vaccine trial concepts. Thus, a comprehensive approach to educating communities and trial participants may help to improve community and participants' knowledge about preventive HIV vaccine trials -- especially ongoing trials -- and inform perceptions of trial-related risks and benefits.

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