Clinical trials are research studies that test whether new medical treatments, drugs, or devices are safe and effective in people. Every approved medication, vaccine, and medical device in use today went through clinical trials before reaching patients. These studies are conducted at hospitals, universities, and research centres worldwide, and are regulated by government agencies to protect participants.
What Is a Clinical Trial?
A clinical trial is a structured research study involving human volunteers. Trials follow a detailed plan called a protocol, which outlines who can participate, what procedures will be done, how long the study lasts, and what outcomes will be measured. Protocols are reviewed by independent ethics committees before any participant is enrolled.
Trials are typically sponsored by pharmaceutical companies, government agencies (like the NIH in the US or NHMRC in Australia), universities, or medical institutions. The sponsor funds the research, but the study is conducted by qualified investigators — usually physicians and research staff — at clinical sites.
The Four Phases of Clinical Trials
Phase 1 trials test a new treatment in a small group (20–80 people) to evaluate safety, determine a safe dosage range, and identify side effects. These are often the first time a treatment is tested in humans.
Phase 2 trials expand to a larger group (100–300 people) to determine effectiveness and further evaluate safety. Researchers begin to understand whether the treatment works for the intended condition.
Phase 3 trials involve large groups (1,000–3,000+ people) across multiple sites. These studies confirm effectiveness, monitor side effects, compare the new treatment against existing standard treatments, and collect information to allow the treatment to be used safely. Phase 3 results are what regulatory agencies (FDA, TGA) use to decide whether to approve a treatment.
Phase 4 trials happen after a treatment has been approved and is on the market. They gather additional information about long-term risks, benefits, and optimal use in broader populations.
What Happens When You Join a Trial
Before joining, you go through a screening process where the research team checks whether you meet the study's eligibility criteria — these are specific requirements related to age, medical history, current health, and other factors.
If you qualify, you review and sign an informed consent document. This document explains the study's purpose, procedures, risks, benefits, and your rights as a participant. Signing consent does not commit you permanently — you can withdraw from a trial at any time for any reason.
During the trial, you follow the study protocol, which may include taking a medication, attending scheduled visits, undergoing tests, and reporting how you feel. The research team monitors your health throughout. After the treatment phase ends, there is usually a follow-up period to track long-term outcomes.
Who Oversees Clinical Trials?
Multiple layers of oversight protect participants. Institutional Review Boards (IRBs) in the United States and Human Research Ethics Committees (HRECs) in Australia review and approve every trial protocol before it begins. The FDA (US) and TGA (Australia) regulate clinical trials involving drugs and devices.
During the trial, a Data Safety Monitoring Board (DSMB) — an independent group of experts — periodically reviews the data to ensure participant safety. If safety concerns arise, the DSMB can recommend pausing or stopping the trial.
Frequently Asked Questions
Are clinical trials safe?
Clinical trials have multiple safety protections including ethics committee review, informed consent, ongoing monitoring by data safety boards, and government oversight. However, all medical treatments carry some risk, and investigational treatments may have unknown side effects. The consent process ensures you understand the risks before participating.
Do I have to pay to participate in a clinical trial?
In most trials, the investigational treatment and related medical tests are provided at no cost. Some trials also reimburse participants for travel expenses. However, routine medical care that you would receive regardless of the trial may still be billed to your insurance. The study team will explain costs during the consent process.
Can I leave a clinical trial once I have joined?
Yes. Participation is voluntary and you can withdraw at any time for any reason without penalty. Your standard medical care will not be affected by your decision to leave a trial.
Will I receive a placebo instead of real treatment?
Some trials use placebos, but this varies by study design. In many trials, all participants receive active treatment — some get the new treatment while others get the current standard of care. The study team will explain the design before you consent. Trials for serious conditions rarely use placebos without also providing standard treatment.
How do I find clinical trials I might be eligible for?
You can search public registries like ClinicalTrials.gov or ClinicalTrialsFinder.org by condition, location, or keyword. Your doctor may also know about trials relevant to your condition. Major hospitals and academic medical centres often have clinical trial offices that can help match patients with appropriate studies.