The concept of vulnerability means something different in an IRB context than it does in the common usage of the term: a vulnerable participant is someone who, due to personal limitations, group memberships, or a situation they are in, might not be completely free to refuse to participate in a research study because they have reduced capacity to make decisions for themselves. Vulnerability in this sense is important because if a person is not completely free to refuse to participate in research, in a sense they cannot give meaningful consent or assent to participate either. Vulnerability is thus tied to the "voluntariness" aspect of consent.

Vulnerability can also be tied to the "comprehension" aspect of consent. In order to weigh one's participation-related options fully, one must understand both the probability and the likely magnitude of potential harm along with other kinds of information about the research experience. Even if information about the research is presented in a comprehensible way, someone who does not comprehend the information cannot freely consent to participate in the research, since they do not understand that to which they are consenting. 

We may talk of vulnerable individuals or vulnerable populations, but in either case, the vulnerability is often due to one of the following conditions/situations (described in a document previously available from the University of Virginia):

1) Cognitive or communicative (e.g., a mental or language barrier; someone who does not speak English or is educationally disadvantaged, or is a child and thus not mature enough to understand the nature of the research, or is a developmentally delayed or mentally ill adult and thus in the same circumstance). Children are discussed on a separate subpage. Someone without cognitive or communicative barriers, but who is in an emotional state where they are not able to think clearly about or advocate for their own interests, could also fall into this category. Someone may also fall into this category if the voluntariness and comprehension conditions are met but the person is unable to express their choice about participating effectively for some reason.

2) Institutional (a student participating in a professor's research or an employee in an employer's research; in this instance, the researcher has power over the potential participant and could theoretically use that power in retribution if the potential participant elected not to participate; similar reasoning is used in describing prisoners, inpatients, and other institutionalized people such as the elderly (in some cases) as vulnerable)

3) Deferential (the researcher is a doctor and the potential participant is a patient, or the researcher is a senior family member; in these circumstances, the researcher is generally treated with special respect and deference and it is presumed that they will get their wishes)

4) Medical (the potential participant has a serious or terminal illness and thus has a medical need that they can only get met by participating in the research; alternately, a person who is depressed or otherwise emotionally upset as a result of their medical situation may not have the capacity to act in their own best interests). 

5) Economic (the potential participant is poor, homeless, or otherwise economically disadvantaged and the incentives to participate (free resources) would make such a difference in the person's life or well-being as to have a coercive effect). The issue of incentives is discussed on a separate subpage.

6) Social (a person is a member of a social group that faces real or perceived discrimination and thus is unusually vulnerable to coercion in a research context). Undocumented immigrants, for example, may face a legal threat if they refuse to participate in research. 

Prisoners, in particular, require special review on the part of the IRB including the presence of a prisoner representative during the Full Board review of the research. Prisoner representatives can include a former prisoner, a social worker with experience working with prisoners, a public defender, a prison chaplain, or an advocate of another generally accepted type. Students may only pursue research involving prisoners as part of a project for which a faculty or staff member is the principal investigator. Faculty and staff are advised that such projects will call for a slow review process compared to our traditionally efficient turnaround.

Additional guidance on research with prisoners is available from the government.

Particularly in the case of biomedical research, pregnant women and fetuses are federally defined as vulnerable but this situation of vulnerability is not discussed here because Colorado College researchers do not currently carry out biomedical research involving pregnant women or fetuses.

None of the above points should be taken to mean that someone with one of the above identities or in one of the above situations can never participate in research, only that they are to receive special protections to make sure that they do in fact consent, have not been coerced, and understand clearly what participation in the research entails.