The HVTN503/Phambili HIV vaccine trial: a comparison of younger and older participants

Abstract

By comparing younger to older participants enrolled in a HIV vaccine efficacy trial, we aimed to gain insights into the inclusion of adolescents in future trials. This was a sub-analysis of a multisite HIV vaccine randomized clinical trial in South Africa, conducted January–September 2007. Motivations for trial enrolment, social harms, adverse events and loss to follow-up were compared between younger (18–20 years old) and older participants (21–35 years old). Both younger (n = 238) and older participants (n = 563) were equally likely to report enrolling for altruistic reasons. Younger females were less likely than older participants to join for trial reimbursement (p = 0.005), while younger males were more likely to enrol because the vaccine may provide protection from HIV-acquisition (p < 0.001). There were no significant differences in the number of social harms reported. Compared to males over 20 years old, 18–20-year-old females were less likely to experience adverse events (OR = 0.1, CI 0.01–0.80) and no more likely to be lost to follow-up (OR = 0.7, CI 0.39–1.25), while 18–20-year-old males were no more likely to experience adverse events (OR = 1.3, CI 0.58–2.83) or loss to follow-up (OR = 0.8, CI 0.51–1.41). Our data support the inclusion of younger participants who are at risk for HIV in future HIV vaccine efficacy trials.