Understanding Informed Consent

How does the informed consent process work in vaccine trials?

AIDS vaccine candidates must be tested in human volunteers to evaluate their safety and efficacy. A vaccine trial can only be successful if people in the community are willing to volunteer for the trial, receive the vaccination, and return to the trial site for follow-up visits. An essential part of running ethical research is assuring that the rights of these volunteers are protected.

To ensure that the volunteer enrollment in vaccine trials meets high ethical standards there is a process known as informed consent. During this process trial investigators must fully explain the details of the trial and the vaccine candidate that will be tested, make sure that the volunteer understands the information, and allow the potential volunteer to freely decide if they wish to participate. The informed consent process must be completed for each person before he or she can enter the screening process for the trial. During the screening process all volunteers undergo research voluntary counseling and testing (see April Primer on Understanding Research Voluntary Counseling and Testing) for HIV infection because only people who are not infected with HIV can enroll in a preventive vaccine trial.

At the end of the informed consent process, everyone who chooses to join the trial is asked to sign the informed consent document that has all this information in writing. The document shows that they want to participate in the trial, but informed consent involves much more than simply signing a paper. The United Nations Joint Programme on HIV/AIDS (UNAIDS) established a set of guidelines that recommends cooperation between researchers, community representatives in the form of Community Advisory Boards (see May Primer on Understanding Community Advisory Boards), and regulatory bodies to design and implement the informed consent process at AIDS vaccine trial sites throughout the world. The protocol for a vaccine trial, including the informed consent document, must receive approval from a local ethics committee and national regulatory authority before that trial can begin.


Community outreach is the first step of the informed consent process and aims to prepare a community for a vaccine trial. All the educational materials about HIV and AIDS vaccines are a necessary first step in getting people informed and interested in participating in a trial. This general information includes what HIV is, how it is transmitted, and how an AIDS vaccine might work. When members of the community who may be interested in volunteering come to the trial site, they are educated about the trial and the vaccine candidate being tested.

The nurse or counselor at the trial site begins by explaining any general background information about HIV and then explains why the vaccine candidate is being tested, what participation in the trial involves, and how the trial is being conducted. For example in some trials, not every person in the trial will receive the vaccine candidate. Some volunteers will receive an inactive substance known as placebo, so that the researchers can compare the vaccine being tested to something they know will have no effect. In most trials, neither the volunteers nor the researchers will know who receives the vaccine candidate or placebo until the end of the trial (this is called a "double blinded" study). The nurse or counselor explains that the person can't be infected with HIV from the vaccine candidate and also emphasizes that the vaccine being tested may not provide any protection against HIV infection and so all volunteers must avoid risk behaviors.

The information provided also includes specifics about the trial process, including the length of the trial, the number of visit to the site, and what medical tests (such as the collection of blood samples) will be required. Potential volunteers will also be informed about the type of general healthcare they will receive during the trial, any reimbursement they will receive for traveling to the site, and most importantly, their right to leave the trial at any time.

The way this information is provided varies based on the trial site, but informed consent documents used in developing and developed countries are very similar. At some sites the informed consent process can extend over several visits, allowing the volunteers to take the information home and discuss it with their family. Once the trial site staff are trained, it is their responsibility to carry out informed consent process according to international and local standards.

Researchers may use videos or flip charts to explain complex issues like the benefits and risks of participation in the trial. The possible benefits include the medical attention that volunteers receive, as well as the rewarding feeling of participating in research that will benefit the community. Potential risks of participating in a vaccine trial include the possibility of side effects of the vaccine candidate or the possibility of temporarily having a false positive HIV test in the future, even though they are not HIV infected. A false positive can occur because the vaccine may cause the person's immune system to make antibodies to HIV, which is what the standard tests measure.

Cultural considerations

Investigators at the site do their best to explain terms in a way that is easy for the individual to understand and should try to answer all questions to the best of their ability. This is an important part of obtaining "true" informed consent. Researchers must be able to explain complicated terms to potential volunteers in a way that is relevant to the community and can easily be understood, sometimes even in languages that have no translations for these words.

The local ethics board as well as Community Advisory Boards have input into the informed consent process before the trial protocol is implemented and can therefore influence this process. Leaders in the community can provide the investigators with culturally-specific ways to explain key concepts. But it is still very important that researchers uphold the standards of the informed consent process, while trying to make it more sensitive to the beliefs of the community.


The final step of the informed consent process involves ensuring that each individual fully understands the information provided. At some sites investigators may use written tests to verify their understanding. The investigators also try to ensure that each person's decision to participate is truly voluntary. The potential volunteer must not be pressured into enrolling by anyone at the trial site, or anyone in their family or community. This can be difficult in some cultures where, for example, women are unable to make decisions without consulting their husbands or community leaders. The nurses our counselors at the trial site should do their best to find out if each person's decision was made independently.

After they are certain the choice was made independently and based on a firm understanding of the trial, the informed consent document can be signed. If the volunteer cannot write, he or she may be identified in another way, such as a thumbprint. Volunteers that complete this step can enter the screening process, where they are examined and tested to see if they are eligible for the trial.