Clinical Trial FAQs

What is a Clinical Trial?

A clinical trial is a research study that tests new ways to prevent, detect, diagnose or treat diseases. Clinical trials help determine whether investigational vaccines, medicines or new uses for existing medicines are safe and effective. Clinical trials are necessary to find potential medicines and vaccines to treat disease and improve health. Clinical trials are also known as intervention studies, clinical studies and clinical research.

The Risks of Clinical Trials

Clinical trial participation involves risk, so it is important that you speak to your physician as well as the trial physician before you decide if participation is right for you. There may be unpleasant, serious or even life-threatening side effects to treatment, treatment may or may not be effective for the participant and participation in the trial may require more time and attention than would be required outside of a clinical trial. This may include travel to trial sites, more treatments, hospital stays or complex dosage requirements.

Before considering whether to participate in a clinical trial, you should know as much as possible about the trial and feel comfortable asking questions about the trial, the expected care during the trial and the costs involved. We invite you to spend time exploring the site to learn more about our clinical trials.

Phases of a Clinical Trial

Phase 1

Phase 1 clinical trials test the medicine or vaccine in a small group of 20 to 100 volunteers who are usually healthy, but not always. The trial often takes place in a hospital. The goals are to determine:

  • If the medicine or vaccine is safe
  • If there are any side effects
  • How the medicine is broken down by and discharged from the body
  • How much medicine is needed and how often
  • For a vaccine, researchers see if it causes the desired response from the body's immune system

Phase 1 trials can take from six months to one year to complete

Phase 2

Phase 2 clinical trials test the vaccine or medicine in approximately 100 to 500 volunteers. In the case of medicines, volunteers usually have the disease or condition the investigational medicine is designed to treat. In vaccine studies, the volunteers are usually healthy. The goals of this phase are to determine:

  • How well the medicine or vaccine works
  • If the medicine or vaccine is safe
  • If there are any side effects
  • How much of the medicine or vaccine is needed and how often

Phase 2 trials can take from six months to one year or more to complete

Phase 3

Phase 3 clinical trials can test the medicine or vaccine in 1,000 to 5,000 patient volunteers. For medicines, volunteers have the disease or condition the medicine is designed to treat. In vaccine studies, the volunteers may be healthy or have diseases or conditions. Phase 3 trials take place in hospitals, clinics or physician offices. Researchers closely monitor patients at regular intervals to:

  • Confirm that the medication or vaccine is effective
  • Identify and monitor side effects
  • Compare the medicine or vaccine to commonly used treatments

Phase 3 trials can take from one to four years to complete, depending on the disease, length of study and the number of volunteers

Phase 4 (On-going Trials)

Phase 4 clinical trials are conducted after the medicine or vaccine has been approved by the appropriate government and regulatory agencies and is being marketed. Researchers continue to gather information about the medicine or vaccine and its safety, side effects and effectiveness.

Marketed products also are studied for new indications. Thousands of people usually participate in ongoing trials.

Frequently Asked Questions

Choosing to participate in a clinical trial is a personal decision, and it is important to gather as much information as possible to make an informed decision. The following frequently asked questions provide information that you may find helpful as you consider participation.

Where do the ideas for clinical trials come from?

Ideas for clinical trials usually come from researchers. Researchers first test new therapies or procedures in the laboratory and in animal studies. The potential treatments with the most promising laboratory results are moved into clinical trials. During a trial, more and more information is gained about a new possible treatment, its risks and how well it may work.

Who sponsors clinical trials?

Clinical trials are sponsored (i.e. funded) by organizations or individuals: physicians, medical institutions, foundations, voluntary groups, and pharmaceutical companies, as well as federal agencies such as the National Institutes of Health (NIH), the Department of Defense (DOD), and the Department of Veteran's Affairs (VA). Trials can take place in a variety of locations, including hospitals, universities, doctors' offices or community clinics.

What is a protocol?


What is a placebo?


What is a control or control group?

A control is the standard by which experimental observations are evaluated. In many clinical trials, one group of patients will be given an experimental drug or investigational treatment, while the control group is given either a standard treatment for the illness or a placebo.

What are the different types of clinical trials?

  • Treatment trials test new possible treatments, new combinations of drugs, or new approaches to surgery or radiation therapy.

What are side effects and adverse reactions?


As a clinical trial participant, how is your safety protected?



Every clinical study in the U.S. must be approved and monitored by an Institutional Review Board (IRB) to make sure the risks are as low as possible and are worth any potential benefits. An IRB is a committee of physicians, statisticians, community advocates, and others that helps ensure that a clinical study is conducted in an ethical manner and the rights of study participants are protected. All institutions that conduct or support biomedical research involving people must, by federal regulation, have an IRB that initially approves and periodically reviews the research.

What is informed consent?

Informed consent is the process in which researchers communicate with potential and enrolled participants about a clinical study. It provides the potential benefits as well as the risks to the patient. It informs the patients that participation in the trial is voluntary, and they may discontinue participation at any time.

The goal of the informed consent process is to protect participants. It begins when a potential participant first asks for information about a study and continues until the study ends.

How should you prepare for the meeting with the research coordinator or doctor?

  • Plan ahead and write down possible questions to ask. 

Will you continue to work with your primary healthcare provider while in a trial?

Yes. Most clinical trials provide short-term treatments related to a designated illness or condition but do not provide extended or complete primary healthcare. In addition, by having the healthcare provider work with the research team, you can ensure that other medications or treatments will not conflict with the protocol.

Can you leave a clinical trial after it has begun?

Yes. You can leave a clinical trial at any time. When withdrawing from the trial, you should let the research team know about it, and the reasons for leaving the study.

What is an "expanded access" protocol?



Source for all questions: CISCRP

Clinical Trials: Important Information to Consider

There is a lot to consider when deciding whether to participate in a clinical study. Any clinical study includes risks, which the study doctor will review with you. Make sure you understand the risks before participating.