Africa's First Large-Scale HIV Vaccine Study Launched

February 12, 2007 - On February 8, 2007, HIV vaccine study collaborators in the United States and the Republic of South Africa announced the launch of the first, large-scale study to evaluate a candidate HIV vaccine on the African continent. The trial will involve up to 3,000 participants at five sites throughout South Africa, and is expected to continue for four years.

The sites are part of the HIV Vaccine Trials Network (HVTN), headquartered at the Fred Hutchinson Cancer Research Center in Seattle, Washington, and supported through a cooperative agreement with the National Institute of Allergy and Infectious Diseases (NIAID) of the National Institutes of Health (NIH) within the U.S. Department of Health and Human Services (HHS). The trial sites also receive funding from the South African AIDS Vaccine Initiative.

"This trial will answer several major scientific issues that face all of us in the field of HIV vaccine development," said Lawrence Corey, M.D., principal investigator of the HVTN, and a member of the Hutchinson Center's Clinical Research Division. "It will determine the usefulness of vaccines that induce high immune response to the parts of the virus that are similar between different strains of HIV-1."

The study is known as a phase II-b, or "test of concept" efficacy trial, because it enables researchers to determine whether the test vaccine prevents HIV infection, results in lower HIV levels in those who become infected after vaccination, or both. In addition, investigators for the South African vaccine trial will determine if this vaccine, based on clade-B HIV, has the potential to protect against the clade-C virus, the subtype prevalent in South Africa.

"Our best hope of ending the AIDS epidemic is a safe and effective vaccine," said the Director of HHS/NIH, the Honorable Elias A. Zerhouni, M.D. "To achieve that goal requires the concerted effort of governments, scientists, and private industry, as well as participation by well-informed volunteers."

"We applaud the South Africans for bringing this important trial to fruition. This international partnership exemplifies the model of collaboration needed to defeat HIV/AIDS," said HHS/NIH/NIAID Director Anthony S. Fauci, M.D.

The South African study is also likely to provide important new data on how the test vaccine might work in a predominantly heterosexual HIV epidemic, how well the vaccine works in women, and whether the vaccine works in populations with pre-existing immunity to the viral vector used in the vaccine, according to Corey, who is also head of the Infectious Diseases Program and Virology Division at the University of Washington School of Medicine.

Merck & Co., Inc., manufacturers the test vaccine, known as the MRKAd5 HIV-1 trivalent vaccine, which has already undergone studies for several years in phase-I and -II trials that have involved thousands of volunteers in the Americas, Africa and Australia to evaluate safety and immune responses. Those previous trials found the vaccine to be safe and to stimulate cellular immune responses against HIV in more than half of volunteers.

Merck Research Laboratories developed the test vaccine, based on an adenovirus—a common cold virus modified so it cannot cause a cold in humans or be passed from person to person. The adenovirus is the carrier, or vector, which transports copies of three HIV genes called gag, pol, and nef. The vaccine is made in the laboratory, and does not contain live HIV. The test vaccine, therefore, cannot cause infection.

The hope of the trial is that these HIV genes will produce a cellular immune response to HIV, and cause the body to make killer cells programmed to recognize and destroy cells infected with HIV. The studies already completed with this vaccine suggest it is generally well-tolerated, and that the response of the immune system, or immunogenicity, is high.

The South African Medicines Control Council and the South African Department of Agriculture have approved the trial, and the HHS Food and Drug Administration has reviewed it. Institutional ethics and bio-safety committees at all the trial sites have given approval, or approval is pending. In addition, there will be an independent Data and Safety Monitoring Board, a group of independent experts not affiliated with Merck & Co. Inc., the HVTN, or the clinical trial investigators, who will carefully monitor the safety of the trial participants.

For more information:

• First Large-Scale HIV Vaccine Trial in South Africa Opens (National Institutes of Health)

Last revised: August 14, 2007