Abstract
The concept of vulnerability has long played a central role in discussions of research ethics. In addition to its rhetorical use, vulnerability has become a term of art in U.S. and international research regulations and guidelines, many of which contain specific provisions applicable to research with vulnerable subjects. Yet, despite the frequency with which the term vulnerability is used, little consensus exists on what it actually means in the context of human subject protection or, more importantly, on how a finding of vulnerability should affect the process of research ethics review.The Common Rule, the centerpiece of the U.S. human subject protection regulations, uses the word vulnerable three times. First, it provides that institutional review boards that regularly review research involving a vulnerable category of subjects should consider including one or more individuals who are knowledgeable about and experienced in working with these subjects.