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Potentially vulnerable study participants – guidance

Studies involving potentially vulnerable participants must be reviewed by the Health and Disability Ethics Committee (HDEC).

An application for HDEC review must clearly explain how risks to potentially vulnerable participants will be minimised.

Definition of potentially vulnerable

The NEAC Guidelines for Intervention Studies defines vulnerable people as those who have restricted capability to make independent decisions about their participation in a study.

The definition also covers people who:

  • may be unable to consent freely to participating in the study
  • may be particularly susceptible to harm because of their health status, physical or mental capacity or employment status, or as a result of imprisonment.

Examples of potentially vulnerable people

It is important to remember that, even if a group is identified as likely to be vulnerable, not all individuals of that group may be vulnerable or, if they are, they may be vulnerable only intermittently. For more information refer to the guide where available.

  • Children and young people (for more information on studies involving children and young people, read the guidance on Children and young people guidance.)
  • Older adults (for more information on older adults, read the guidance on Older study participants.
  • People with a mental illness.
  • People with a serious intellectual disability, read the the guidance on study participants with an intellectual disability.
  • People with English as a second language and/ or a different cultural background to the investigators (for studies whose details are primarily, or only, stated in English).
  • People whose freedom to make independent choices is restricted (for example, prisoners, employees of a sponsoring company or students), read the guidance on Specific categories of healthy study participants.
  • People with serious illnesses for which the study treatment offers potential benefits that substantially exceed those of any other available treatment, read the guidance on Terminally ill study participants.
  • Participants who cannot provide their informed consent, such as unconscious people.


The benefits and burdens of participating in a study must be distributed fairly across a population and across participants from that population.

Thus, vulnerable members of a community who are participating in a study that will benefit other members of the community should not bear a disproportionate burden of that study (paragraph 4.5 of the NEAC Guidelines for Intervention Studies and 4.8 of the NEAC Guidelines for Observational Studies).

Informed consent

Study participation should be a matter of free and informed decision-making by study participants wherever possible. (Also refer to the Code of Rights, Right 7(2) and (3); and paragraph 5.35 of the NEAC Guidelines for Intervention Studies.)

When a vulnerable person is capable of deciding for themselves whether to participate in a study, that person’s decision should be respected. Refer to specific pages for advice around obtaining consent from children.


Vulnerable people should have the opportunity to participate in high-quality studies on questions that might affect their health, taking the following into account.

  • The study should ask questions that matter to the participant’s group, and the answers should benefit that group.
  • Studies should not involve vulnerable groups if other groups would be adequate.
  • Studies that involve a vulnerable group should involve the least vulnerable people in that group (for example, older rather than younger children).
  • Intervention studies should be conducted only if the risk to vulnerable people is at an acceptable minimum.

Studies involving vulnerable people might require additional support (for example, extra time, resources – such as modified information sheets or means of information delivery – and assistance) to ensure that such people are able to participate fully.

The interests of vulnerable participants must be protected, and the participants must not be exploited for the advancement of knowledge. This is an especially important consideration if any of the interventions being studied are invasive.

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