Clinical trials: Parents’ experiences

Side effects in clinical trials

Clinical trials are carefully designed to minimise the risks and maximise the benefits to everyone taking part, whichever treatment they receive. Some trials will involve very little risk. Researchers should explain to you what they already know about possible side effects to help you decide whether, or not, to enrol your child. This will depend very much on the type of treatment being tested, so you will need to ask questions about the specific trial. Of course, it can be worrying hearing about all the possible side effects. However, it is important to bear in mind that usually few people will experience them.
Most parents said that possible side effects of treatment were explained to them and they were able to ask questions and raise any concerns. (See also ‘Information given to parents when invited to enrol their child’.)
Some parents in vaccine trials remembered the recent debate on the MMR vaccine. (See also Immunisation - parents concerns about MMR). Catherine’s son was born prematurely and she decided not to enrol her son in a five-in-one vaccine trial.
However, most people with children in vaccine trials reported few side effects, mostly were minor symptoms such as soreness and a raised temperature. Knowing what to expect was reassuring for parents, as in Lena’s case, they didn’t feel the need to phone the researchers or seek further medical advice.
One of the main reasons for carrying out trials is to find out about side effects and measure how serious they are. Children who take part in trials are monitored carefully. They will often require regular tests and may be asked questions about how they feel. Lucinda was initially concerned that her son would not be able to tell the doctors about any side effects.
Jo rang the doctors immediately when her son began to change his behaviour.
It is important to report any side effects promptly as this tells the researchers something important about treatments being tested. They will be able to help manage the side effects, or advise you whether your child should stop taking part. As Jo (above) says it is not always clear to parents whether symptoms are a result of the trial or just coincidence, but it is better to tell the doctors. Withdrawing from a trial because of side effects is entirely reasonable and no-one should feel they have to stay in for the sake of the trial or that they have failed if they pull out. (See also ‘Withdrawing your child from a trial’.)
One parent talked about her son’s experiences of side effects while taking part in a Phase 1 trial. However, Alison’s son is at an age when he can consent to take part and this has been worrying for her at times.
In all trials the treatment may cause side effects or problems that doctors cannot predict. This may happen more often when less is known about the treatment being tested as in the Phase 1 trial for Alison’s son. (See also ‘When the trial ends: feedback of trial results’.)

Anyone taking part in a drug trial should also be told about other drugs or other substances, such as food or herbal remedies, which may interact with the trial drug and cause side effects. Sometimes trials that do not involve drugs can also have side effects, for example minor surgery or tests that may leave your child feeling uncomfortable. Several parents said their children found blood tests and injections difficult. This is discussed in ‘What is involved in a trial: appointments and monitoring’).  

Last reviewed September 2018.
Last updated June 2013.



Please use the form below to tell us what you think of the site. We’d love to hear about how we’ve helped you, how we could improve or if you have found something that’s broken on the site. We are a small team but will try to reply as quickly as possible.

Please note that we are unable to accept article submissions or offer medical advice. If you are affected by any of the issues covered on this website and need to talk to someone in confidence, please contact The Samaritans or your Doctor.

Make a Donation to

Find out more about how you can help us.

Send to a friend

Simply fill out this form and we'll send them an email