Objective:  Vulnerability is a central concept in protecting both the rights and the welfare of human subjects in research.  The current standards by which we determine a vulnerable population has been argued by ethicists to be both narrow and broad in scope.  The objective of this study was to develop a conceptual framework for better understanding the characteristics of vulnerability in clinical trial research, focusing on AIDS Clinical and HIV Prevention Trials.

Methods:  Study design was cross-sectional and exploratory, using qualitative methods.  A total of 19 study coordinators and 19 investigators from AIDS Clinical Trial Units (ACTUs) and the HIV Prevention Trial Network (HPTN) participated in this study.  Telephone interviews were conducted with each participant.  Participants were asked to define vulnerable populations, and provide feedback on the current categories of vulnerable populations with special protections identified in 45 CFR 46, subparts B, C, and D.  Audiotapes of the interviews were transcribed to text and analyzed qualitatively.  Text analysis yielded a conceptual framework exploring vulnerable populations in HIV/AIDS clinical and prevention research.

Results:  Social, research-oriented, or HIV/AIDS-specific characteristics were elicited when asked the question defining a vulnerable population.  Social characteristics included substance abuse, and being economically disadvantaged.  Research-oriented vulnerabilities included not understanding the process of research, or what is required of them as study participants.  And, HIV/AIDS-specific vulnerabilities included experiencing stigma, and lacking access to HIV care and treatment.  Although participants agreed that the categories of vulnerability delineated in the regulations were acceptable, they identified examples of overprotection for, or reasons why pregnant women, prisoners, and children should not always be considered vulnerable in research.

Conclusion:  This study broadens our understanding of vulnerable populations by exploring the perspectives of HIV/AIDS researchers, and the conceptual framework developed challenges current thinking about the current categories of vulnerable populations for which special protections are stated.