Preventive trials
Why develop a preventive vaccine against HIV?
The development of a preventive vaccine against HIV represents the best solution for controlling and eradicating the HIV pandemic
• Worldwide, over 37 million people are currently infected with HIV, and 1.7 million new cases are reported annually. Less than half of the people living with HIV have access to antiretroviral treatments.
• In France, there are 170,000 infected people—nearly 425,000 of whom are unaware of their status, and continue to spread the epidemic—and 6,200 new cases in 2008.
• Other preventive strategies exist (use of condoms, PrEP: pre-exposure prophylaxis with antiretrovirals); however, the medical/scientific community agrees that only a combination of these strategies with a preventive vaccine will make it possible to control the growth of the epidemic of HIV infection
What types of clinical trials on preventive vaccines against HIV are currently being conducted by the VRI?
The trials currently being developed by the VRI are phase I and II clinical trials.
Development of a vaccine requires, after testing in animals to ensure the absence of toxicity, the establishment of 3 successive phases
• Phase I. At this stage, trials are conducted with a limited number of subjects under strict medical supervision. The vaccine is tested over a short period. The objective is to evaluate its safety of use, its fate in the body, and potential adverse effects.
• Phase II. Trials are conducted on a larger number of subjects. These trials are usually comparative according to the international clinical trial standard settings: one of the two volunteer groups is given the vaccine whereas the other is given a placebo. They are aimed at obtaining data on safety of use for a larger number of subjects, and studying the immunogenicity (induction of an adaptive immune response) of the vaccine. Currently, these phase II trials generally involve testing vaccine combinations of several vaccine candidates.
• Phase III. Trials are conducted on large volunteer populations, to allow measurement of the efficacy of the vaccine, i.e. its impact on the occurrence of infections. These trials are conducted in at-risk populations. Vaccine candidates previously compared with placebo will in future have to be compared with strategies with demonstrated efficacy (particularly PrEP).
How does a clinical trial of a preventive vaccine against HIV ?
What is the period of participation of a volunteer ?
The period of participation of each volunteer generally varies from 6 months to 1 year following enrolment. The volunteers are randomly assigned to the different groups corresponding to the various vaccine combinations being evaluated.
How many visits are needed ?
The number of visits is arranged for each volunteer, depending on the vaccine combination. Generally, 8-10 visits are required, each lasting 1-3 hours to ensure tight supervision of the participants involved in the clinical trial.
What is the 1st medical visit like ?
The first medical visit known as the pre-inclusion visit, takes place 4 weeks before the start of vaccination. It includes questions on the sexual life of the volunteers as well as a full clinical examination and biological tests (on blood and urine samples), to ensure that each volunteer is in good health and does not present a substantial risk of contracting the virus through his/her sexual practices.
What do researchers with blood samples of volunteers ?
Blood samples, anonymously numbered, are taken and frozen to constitute a biobank. They are used to confirm certain biological data, and for the performance of additional tests in the context of the trial. They may also be used, with the consent of the volunteers, for research on the design of vaccines against HIV, Hepatitis C and (re)-emerging infectious diseases.
When do we know the results ?
The overall results are generally known 6 months after the end of the trial, and are sent to the volunteers as soon as they are known.
To know about enrolment in a vaccine trial :
Each volunteer may discontinue his/her participation in a HIV vaccine trial at any time, without giving any reason. Since the numbers in volunteer groups in phase I and phase II clinical trials are quite limited, their withdrawal may compromise or seriously complicate the interpretation of the results of the trial as a whole. It is therefore better for individuals not to enrol if they do not think they can participate until the end.
Is compensation provided ?
Compensation is generally provided for each visit, in order to compensate for the time devoted to the trial.