How useful is 'vulnerable' as a concept?

The relationship between socioeconomic status, ethnicity, and chronic illness, on the one hand, and health status, access to health services, and quality of health care received, on the other, is a central and critical axis of health services research and health policy. However, it is not clear that the use of the term "vulnerable" to apply to individuals, groups, or populations helps very much from either an analytic or a policy perspective. This brief essay explores two instances of "vulnerability" far outside the prevailing paradigm, and it further identifies problems with the term.