A combination of two HIV vaccines reduced the risk of infection by almost one-third in a large trial in Thailand, the trial sponsor announced today. It is the first proof that a vaccine against HIV can protect against infection, but scientists say a lot more research will be needed before a vaccine emerges that can be given to large numbers of people.
“This is a historic day in the 26-year quest to develop an AIDS vaccine,” said Dr Alan Bernstein, executive director of the Global HIV Vaccine Enterprise.
"This is the first HIV vaccine candidate to successfully reduce the risk of HIV infection in humans. We are very excited and pleased with the outcome of this trial and congratulate all those who participated in it," said Lieutenant General Eric Schoomaker, Surgeon General, U.S. Army, the trial sponsor.
The trial, called RV 144, compared a regimen of vaccination with two products against vaccinations with a dummy, inactive substance in 16,000 adults enrolled since 2003.
The study recruited adults in the community in two provinces of Thailand with high HIV prevalence (Chon Buri and Rayong), but did not specifically target individuals at high risk of HIV infection. Volunteers for the study were adults aged 18-30 who gave informed consent to participate in the trial.
Participants were randomly assigned to receive an initial set of vaccinations with ALVAC, and follow-up booster vaccinations with AIDSVAX, a product previously tested in large trials without evidence of success, or the placebo vaccination.
The presence of AIDSVAX in the vaccination regimen was one reason why many vaccine experts had not expected the trial to show a positive result.
In the event, the prime-boost combination of ALVAC(R) HIV and AIDSVAX(R) B/E lowered the rate of HIV infection by 31.2% compared with placebo. This reduction was statistically significant, meaning that the possibility that the possibility of the result being due to chance is very low, but the confidence intervals for the estimate in the reduction in risk were wide (p=0.039, 95% confidence interval 1.1% - 51.1%).
In the final analysis, 74 placebo recipients became infected with HIV compared to 51 in the vaccine regimen arm. The vaccine regimen had no effect on the amount of virus in the blood of volunteers who became HIV-infected during the study.
More detailed results of this study will be presented next month at the AIDS Vaccine Conference, October 19 - 22 in Paris, France.
The vaccine products used in the study will not go forward for immediate licensing. Instead, the results from the study, which was considered to be a `proof of concept` trial, will be used to inform the design of future vaccine trials.
Collaborating partners on this study include the U.S. Army, the Thai Ministry of Public Health, the United States National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health, sanofi pasteur (the developer of ALVAC), and Global Solutions for Infectious Diseases (GSID), the current developer of AIDSVAX. The collaborators are already working with external experts to determine the need for additional studies on this vaccine regimen and consider the impact of this study’s findings on other HIV vaccine candidates.
More information and analysis
See also An unpopular vaccine study produces surprising result.
See also Vaccine trial "is the beginning" of a new path of research, says US health chief.
See aidsmap.com's guide to The search for an HIV vaccine for further background information.
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