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Are clinical trials safe?

Are clinical trials safe?

Medications and vaccinations allow us to live healthier, longer lives, but it takes a lot of research for new treatments to be approved. All new drugs and jabs have to be thoroughly tested before they are allowed to be prescribed, which requires people to take part in clinical trials. Although these trials may sound scary, scientists go to great lengths to ensure they are safe. But how?

How do researchers ensure clinical trials are safe?

Any drug, vaccine, or medical device has to go through many stages of testing in laboratories before it can begin to be trialled on people1.

All trials are strictly monitored to make sure that everyone involved is protected. Each trial also has a sponsor who is responsible for running the trial, which may be the organisation funding it, a hospital, or a university.


First, researchers develop a protocol, which is essentially a detailed plan for the trial. Everyone involved in the trial must stick to the protocol, which helps to keep the participants safe.

The protocol outlines the purpose of the study, the goals, how many volunteers are needed, the medications or methods involved, how long the trial will last, and the type of information the researchers will collect.

Trial monitoring

Before a clinical trial of a new treatment can begin, a government agency called the Medicines and Healthcare products Regulatory Agency (MHRA) needs to review and authorise it.

Another group called the Health Research Authority (HRA) also works to protect and promote the interests of patients and the public in health research. It's responsible for research ethics committees, which are independent groups which make sure that a clinical trial is ethical, legal, well-designed and most importantly, safe.

All medical research involving people in the UK has to be approved by an independent research ethics committee.

These groups make sure that medical trials don't involve any unnecessary risk and include a safety plan.

Informed consent

Researchers must also get informed consent from people participating in clinical trials. That means they must make people aware of the details of a trial, including interventions or procedures, the research plan and possible risks or side effects.

Before giving your consent, you’ll be given a patient information sheet, which includes detailed information about the trial to help you decide whether you want to take part. You can also keep this to refer to during the trial. It's your choice whether you want to be in a trial and you can change your mind at any time2.


There are also strict confidentiality rules about who can and can’t see your personal information. Only the clinical and research teams who need to access your records will do so.

What are the risks of clinical trials?

All medicines, vaccines and treatments can have side effects, including those that have been approved. All new treatments carry some risks, but researchers work to minimise these risks during clinical trials.

The risks posed to volunteers in clinical trials depend on what is being tested. For example, someone taking part in a drug trial may face side effects, while other trials may come with minimal risks. Researchers carry out risk assessments so they know what might happen during a trial and how to manage any issues.

However, the benefits of a trial may outweigh the risk. Taking part in a trial may give you access to new drugs - and it can be satisfying to know that you’re contributing to research.

Are some clinical trial phases safer than others?

Clinical trials testing new treatments are placed into different stages called phases. The earliest phase trials - phase 0 or I - may look at whether a drug is safe or the side effects it causes. Later phases - II or III - trials aim to test whether a new treatment is better than existing treatments.

Each phase carries its own risk. Scientists may know less about the treatment in the earlier phases because it has been studied less. However, scientists will have examined the treatment thoroughly in laboratory research before any trials in humans begin.

Further reading

  1. 1. National Institutes of Health: NIH clinical research trials and you.
  2. 2. National Institute for Health and Care Research: Be part of research.
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