Vulnerable Populations

What does it mean to be vulnerable?

There are many possible ways to define who is vulnerable in the research context. Some would include the following: those who are ill (dependent on clinician for care), ethnic or racial minorities, non-English speakers, children, the economically disadvantaged, adults with diminished capacity. If one includes all of these groups, then almost everyone will qualify. The Council for International Organizations of Medical Sciences (CIOMS) International Ethical Guidelines for Biomedical Research Involving Human Subjects provides a succinct and useful defintion; Vulnerable persons are those who are relatively (or absolutely) incapable of protecting their own interests. More formally, they may have insufficient power, intelligence, education, resources, strength, or other needed attributes to protect their own interests.

The CIOMS Guidelines also state that Special justification is required for inviting vulnerable individuals to serve as research subjects and, if they are selected, the means of protecting their rights and welfare must be strictly applied. Investigators need to explain why they have chosen to conduct the research in children or other vulnerable group instead of in a group that is more able to protect themselves. The desire to protect must be balanced with the need to conduct research in order to advance medical science in order to benefit those same vulnerable populations.

Special Protections in the FDA Regulations

The FDA did not any equivalent protections for these population until 2001, when a draft rule created Subpart D protections for children similar but not identical to the Subpart D protections in the Common Rule. The final rule promulgating the Additional Safeguards for Children in Clinical Investigations of Food and Drug Administration-Regulated Products was published in the Federal Register in February 2013. The FDA regulations still do not include the equivalent of the Common Rule's Subparts B or C.

Resources from the National Commission and Related Subpart Regulations

The National Commission issued three reports related to groups deserving of additional protections in the research context provide the basis for the additional protections incorporated into the Common Rule. Many of the recommendations and wording from these reports became incorporated into Subparts B, C and D of 45 CFR 46 (below).

Children in Research
Pregnant Women, the Fetus and Neonates of Uncertain Viability
Research Involving Prisoners
Other National Commission Reports
General References on the Concept of Vulnerability

Most of the research protocols active at CHOP involve children as research subjects. Understanding the regulations governing participation of children in research is vital. Children are neither legally nor developmentally capable of consenting to their own treatment or participation in research. No one can consent for an individual other than that person. As a result, a proxy, such as a parent, must provide permission in lieu of consent and children who are deemed capable, must provide their assent.


There are additional protections and requirements for pregnant women and fetuses' participation in research that is federally funded. These protections are provided in 45 CFR 46 Subpart B: Additional Protections for Pregnant Women, Human Fetuses and Neonates Involved in Research.


Prisoner means any individual involuntarily confined or detained in a penal institution. The term is intended to encompass individuals sentenced to such an institution under a criminal or civil statute, individuals detained in other facilities by virtue of statutes or commitment procedures which provide alternatives to criminal prosecution or incarceration in a penal institution, and individuals detained pending arraignment, trial, or sentencing.


When an adult does not have the capacity to consent to the procedures involved in the research, then they cannot participate without the consent of their legally authorized representative (LAR). In Pennsylvania, a competent adult may designate an individual of their choice to serve as their LAR. If that individual loses the ability to consent due to a temporary situation (surgery, trauma), their LAR may act on their behalf. Someone with a progressive condition such as Alzheimer's can also designate an LAR before they lose the competence to consent.