What are Inclusion and Exclusion Criteria in Clinical Trials?

Without clinical trials, it would be impossible to develop new medicines, cures, vaccines, and other medical products. These research studies test investigational products with human participants to ensure products are adequately safe and effective before they can be offered to the general public.

Medical products with broad use, like over-the-counter medicines or vaccines, tend to be tested in a wide range of people with few restrictions as to who can participate in later phases of clinical trials, while medications or devices designed to help people with specific illnesses or disorders are studied in a more selective groups of volunteers.

In this article, you’ll learn about inclusion and exclusion criteria, and why they are crucial to the clinical research process.

Definitions and Examples of Inclusion and Exclusion Criteria

Every clinical trial has a protocol, which is a document outlining the study design, necessary participants, and more. Protocols include inclusion and exclusion criteria, which are characteristics a person must have (or not have) to be eligible to join a study.

Examples of inclusion and exclusion criteria may include:

  • Age
  • Ethnicity
  • History of disease(s)
  • Smoker or non-smoker
  • Body mass index (BMI)
  • Pregnancy or intention to become pregnant during a study
  • Presence of chronic conditions (e.g., high blood pressure, kidney disease, asthma)
  • Medications taken routinely
  • Recent vaccinations
  • Lack of response to related medications
  • Immune system status
  • Ability to attend study visits and fulfill data collection requirements (usually involves compensation)

In studies conducted by Velocity, enrollment specialists review inclusion and exclusion criteria with each potential patient to determine eligibility. Later, at the patient’s screening visit, study staff will gather medical histories and more from the participants before guiding them through the informed consent document.

Why are Inclusion Criteria and Exclusion Criteria Important?

The main goal in clinical trials is to prove that a medical product is safe and effective in the target population for which it was designed. Therefore, ensuring trial participants are representative of the target population is crucial to the success of the study.

Generally, the inclusion and exclusion criteria of a study change as the trial progresses from phase to phase. For medications, devices, and vaccines intended for broad populations, the inclusion and exclusion criteria in Phase 1 tend to specify young, healthy adults. If trials progress to Phases 2 and 3, older and more sensitive populations may be included.

The way participants were enrolled for The COVID-19 vaccines are a prime example of the way inclusion and exclusion criteria work in clinical trials. In Phase 1 trials, the dozens to hundreds of participants were generally healthy and had no (or well-controlled) underlying medical conditions.

After the initial Phases of the studies showed promise in safety and efficacy, Phase 3 trials welcomed a wider population — from those with underlying conditions, to children and teenagers. All of the studies may have broadened their inclusion criteria in later Phases, but they also had exclusions to help safeguard participants.

Here are examples of inclusion and exclusion criteria from Moderna’s mRNA-1273 COVID-19 vaccine studies:

Determining Your Eligibility for a Clinical Trial

When considering joining a clinical trial, you must meet the qualifying criteria for your safety and the integrity of the study. After filling out the form on our find a clinical trial page, an enrollment specialist will contact you to determine your eligibility and to potentially schedule you for a screening visit. In both of those instances, it’s vital to be honest about your medical history. If you’re not eligible for one study, you may be eligible for another — our enrollment specialists can help match you to studies for which you may be eligible now and in the future.

Velocity has sites across the U.S. and Europe that are conducting research studies across a broad range of therapeutic areas. New studies are added every week. If you’re interested in learning more about, or participating in, a clinical trial near you, visit our find a study page to speak with a recruitment specialist.

More Reading on Clinical Trials

Visit our Learning Center to read all about clinical trials, or click the links below to explore related topics:

It all starts with people like you.

Without clinical trial participants, it would not be possible to create new medicines, treatments, and cures.