A factorial survey study to assess the acceptability of HIV vaccine trial designs

To aid in the design of human immunodeficiency virus (HIV) vaccine trials that maximize volunteer participation, factorial surveys were administered to 73 gay men who were participants in a larger study assessing HIV vaccine trial feasibility. Factorial surveys are "vignettes" that are randomly constructed through the combination of descriptive statements (dimensions) that reflect essential features. In this study, the dimensions define components of clinical trials to assess the efficacy of hypothetical HIV vaccines. Regression analysis shows that anticipated participation was decreased by a sustained vaccine-induced antibody response lasting 3 years, absence of gay men as research subjects in earlier phase trials for the products being tested, and rectal vaccine administration. Three years of scientific experience with the vaccine encouraged participation. We conclude that willingness to participate in vaccine trials varies systematically with some of their characteristics. Where there are design alternatives for identified negative components, these should be considered. If this is not possible, options for decreasing aversion to such features will need to be evaluated, including appropriate education regarding both the benefits and the risks associated with negatively evaluated features.