Volunteer Guidance

Volunteer Guidance for Human Challenge Trial Informed Consent Procedures

One of the most important parts of being in any medical trial is informed consent. That means that a participant not only consents, but does so with all the knowledge and awareness they need to make the decision. If the participant can’t understand the relevant information (or if relevant information were withheld from them), their consent would not truly informed, and it would be unethical (and sometimes even illegal!) to enroll them in a study.

For a medical study of any kind, the informed consent process will help you to understand the risks and benefit so you make a decision about whether to take part in the trial or not. As part of this, you have the opportunity to ask any questions that you might have of the trial team. They will provide you with a lot of information already, but we would draw your attention to a few important aspects and potential consequences of challenge trial participation.


General Advice

challenge study

Things to think about in a challenge study

Questions you may wish to ask for an inpatient study:


Challenge trials often will require participants to stay in secured facilities to prevent the spread of the disease to others (this depends on the disease, though). For airborne illnesses like the flu or COVID-19, this generally means quarantine in an individual room with no outside visitors besides medically trained study staff. For other diseases, you may live in a more dorm-like facility with other participants who you can interact with. Some studies may be completely outpatient if the disease is very hard to spread to others.

Long-Term Effects

Challenge trials are designed to minimize the risk of long-term negative impacts on participants, but no one can ever guarantee that nothing bad will ever happen. Study coordinators will inform you about possible long-term consequences of infection by a disease. Do not be afraid to ask any questions you may have about long-term consequences for any sickness.

The long-term risks of COVID-19 challenge trials are higher than those of Phase III vaccine trials. Long term risks include illness immediately after the trial (lingering symptoms), as well as prolonged illness, commonly referred to as “long COVID”, which could leave you feeling ill for a few months after the trial ends. (1Day Sooner’s summary of research on the long-term effects of COVID-19 is available here.)

Even if they are rare, long-term risks should be a factor in your personal decision to participate in a challenge trial, and you should consider the mechanisms in place for protecting you as much as possible, and possibly compensating you.

Questions you may wish to ask: