In late September, the U.S. federal government announced news on HIV vaccine research that sparked interest around the world. A trial called RV144, or the Thai HIV vaccine clinical trial , showed that the experimental vaccine regimen was safe and about 31 percent effective in preventing HIV infection. Although the vaccine regimen had a very modest effect (typical vaccines for other disease and conditions provide about 80-90 percent protection), it is the first HIV vaccine to demonstrate any ability to reduce the risk of HIV infection in people. Since the discovery of HIV, making a vaccine has been a major scientific goal of AIDS researchers. Until now, the field has been paved with setbacks and disappointments including two trials that were stopped in 2007 due to safety concerns. This new result reminds us that science is about finding answers and to do this, we must continue to conduct research.
As we look at the results from RV144, a key question is what happened to those volunteers who were vaccinated but became infected? The researchers discovered that the vaccine regimen had no effect on the amount of virus in the blood of volunteers who became infected during the study. This clearly begs the question of whether the immune responses needed for preventing infection and controlling the virus are partially related or perhaps completely different. This forces us to acknowledge that we may not have a clear picture of how a vaccine can provide a high level of protection against HIV. We need to learn as much as possible from this study for the design of future vaccine candidates.
It is also important to note that with more than 16,000 participants this was the world’s largest HIV vaccine study to date and was a massive undertaking. The study represents a culmination of years of effort and collaboration between the U.S. Military HIV Research Program , the National Institute of Allergy and Infectious Diseases, the Thai Ministry of Public Health , Sanofi Pasteur , Global Solutions for Infectious Diseases and other partners.
As we move forward, we need to analyze the results of the trial and evaluate blood samples gathered from vaccinated subjects to try to figure out why the vaccine worked in a modest way. From this we can improve the design and make better vaccine candidates. In many ways, this is the beginning of the journey—and we do not yet know exactly where we are going.
Though we are still several years to a decade or more away from a licensed HIV vaccine in the United States, the Thai trial represents an important step in the right direction and renews hope that a safe and highly effective vaccine is indeed achievable.