Interest among gay/bisexual men in greater Boston in participating in clinical trials of preventive HIV vaccines.

To estimate interest in HIV preventive vaccine trials, we administered questionnaires to two otherwise demographically similar cohorts of older (mean 40 years) and younger (mean 23 years) gay men in Boston. Questionnaire responses were linked to concurrent behavioral and demographic data. Univariate analyses, performed separately for older and younger cohorts, identified factors that distinguished participants who were "very interested" from those who were "not at all interested". Multivariate logistic regression analyses were used to adjust for confounding. Among all 630 participants, 215 (34%) were "not at all" interested in participating, 306 (49%) were "somewhat" interested, and 102 (16%) were "very" interested. Older men were significantly more likely than younger men to be "very" interested and less likely to be "not at all interested." Among both older and younger men, perceived peer willingness to enroll in vaccine trials predicted interest after adjusting for confounding. Among older men, optimism about success in vaccine development also predicted interest. In the younger cohort, men recruited in community settings (e.g., bars, nightclubs) were more interested in vaccine trial participation than were those recruited by outreach workers and word of mouth on college campuses. Vaccine-induced seroconversion evoked significant concern.