Considerations regarding efficacy endpoints in HIV vaccine trials: executive summary and recommendations of an expert consultation jointly organized by WHO, UNAIDS and ANRS in support of the Global HIV Vaccine Enterprise.

HIV vaccines of the first generation are, in contrast to most currently licensed vaccines, unlikely to provide sterilizing immunity against infection with HIV. However, they are expected to exert a beneficial effect on the maintenance of CD4 T-cell counts by reducing viral load. There is a recognized need for clarifying the path to licensure of such novel vaccines and defining the clinical trial endpoints. This was the focus of discussions of a 2-day workshop organized by the WHO, UNAIDS and the ANRS, in support of the Global HIV Vaccine Enterprise, which took place in Paris, France (5-6 September 2007). This expert consultation, the proceedings of which are presented here, was intended to review the fundamental principles and approaches to validate surrogate markers in clinical research, as well as the significance of viral load for the individual course of disease and for secondary transmission. Recommendations were also made for additional research to inform decision-making regarding potential licensure and delivery of vaccines which do not prevent HIV acquisition but do reduce viral load.