What are Vulnerable Populations?

Posted March 2, 2018

In the early stages of your research, you will need to decide on a population to study. There are many different factors that may guide the selection of your study population, such as your research aims and the anticipated availability of participants. One important factor that you need to consider in your selection is whether the population is considered a vulnerable population.

So, what exactly is a vulnerable population? A vulnerable population is a group of people that requires greater protection than normal against the potential risks of participating in research. Individuals in vulnerable populations may have a higher risk of negative outcomes as a result of participating in a research study, they may have a reduced capacity or ability to give consent, or they may (for other reasons) have special legal protections. Below is a list of populations that Institutional Review Boards (IRBs) commonly consider to be vulnerable:

  • Children (i.e., minors or individuals under the legal age of consent)
  • Individuals who are incarcerated (i.e., prisoners)
  • Residents of a facility (such as a mental health facility, nursing home, treatment center, etc.)
  • Individuals with a life-threatening illness or condition (e.g., cancer, HIV/AIDS)
  • Individuals with a debilitating mental health condition or cognitive impairment
  • Pregnant women
  • Victims of traumatic events (e.g., abuse, natural disasters)
  • Individuals involved in a crisis (e.g., war, natural disaster)
  • Individuals who are economically disadvantaged
  • Individuals who are not fluent in the language the study is being conducted in (e.g., non-English speakers in studies conducted in the United States)
  • Elderly individuals (e.g., 65 years old or older)
  • Subordinates of the researcher (e.g., students, employees)


If you are studying a vulnerable population, the IRB will often require you to have specific procedures in place to protect your participants. For instance, if you are studying children, you will need to have procedures for obtaining assent from the child, as well as consent from their parent or legal guardian. In any research involving vulnerable populations, the IRB will heavily scrutinize your study, not only in terms of its procedures but also its merit. In other words, you will need to demonstrate to the IRB that your study procedures are ethically sound, that the risks to participants are as minimal as possible, and that the scientific contributions and potential benefits of your study are significant enough to warrant exposing vulnerable individuals to the risks and burden of research participation.

However, even if you demonstrate all of those things in your IRB application, there is no guarantee that the IRB will allow you to conduct the research. In some rare cases, the IRB may not allow you to study a particular population, regardless of the ethical rigor and merit of your proposed research. This is why it is a good idea to have a discussion with your IRB in the early stages of your research if you have any plans to recruit from a vulnerable population. Having this discussion early on may save you from spending months on a proposal that could inevitably be rejected by the IRB.

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