Professor Leonard in the laboratory. Photo by Craig Bailey.
September 29, 2009
Last week researchers announced that a new combination vaccine has been shown to greatly reduce the risk of HIV infection. Here Steven Leonard, assistant professor of pharmacy in the department of pharmacy practice and a specialist in infectious diseases, answers questions about what the results of this groundbreaking study mean for AIDS patients and HIV/AIDS research.
What did researchers discover, and how do their findings fit into the big picture of finding a cure for HIV/AIDS?
By cutting the risk of infection by more than 30 percent, this study is the first to show any benefit whatsoever from an HIV vaccine. It did not completely prevent HIV infection, and more work will be needed before a vaccine would be available, but it is a major step forward.
In the last 25 years since it was determined that the HIV virus causes AIDS, there have been more than 25 million deaths worldwide as a result of the disease. Each year there are 2 to 3 million new cases. While our means to combat the infection and extend people's lives has greatly improved, there is still no cure. So our ability to prevent the infection is key in fighting HIV.
How does this study differ from previous studies?
Aside from being the first to show any efficacy, it differs in that it was a combination of two vaccines given in a sequence of six immunizations over the course of six months. It was based on HIV strains that commonly circulate in Thailand, where the study was conducted. At this time it’s unclear how these vaccines would work elsewhere in the world.
The recent trial was conducted on a test group of 16,000 volunteers. How does the size of this trial compare with previous trials of other vaccines?
It is the largest HIV vaccine study ever. In terms of enrollment, it is similar in scope to recent studies of vaccines against human papillomavirus (HPV) for the prevention of cervical cancer. This lends a good deal of credibility to the results.
What is the likelihood of the HIV vaccine becoming available to the public—particularly to people in developing nations who are most susceptible to the virus?
I believe that if a successful vaccine becomes available we will see a worldwide effort of unprecedented scope to ensure that the vaccine is made available to everyone, including those in developing nations where the impact of the disease has been the most severe. It would be one of the most important advances in public health during our lifetime.
Will we ever be able to vaccinate against HIV/AIDS with the success rate that we have for vaccinating against, say, the mumps or polio?
Before these results were released I was skeptical that a vaccine for HIV/AIDS could be developed. My doubts stemmed from the significant scientific difficulties presented by the virus and the fact that two previous large-scale HIV/AIDS vaccine trials failed to show any benefit. While this vaccine didn't prevent HIV infection completely, it does give a reason to hope that a successful vaccine could be developed in the future.