By C. Todd Lopez
WASHINGTON (Sept. 24, 2009) -- An Army-sponsored study has shown that administration of a specific combination of vaccines can reduce the potential to contract HIV by 31.2 percent.
As part of the RV144 HIV vaccine study, 16,395 adult men and women in Thailand were given either a placebo or the "prime boost" combination of the vaccine ALVAC(R) HIV and the vaccine AIDSVAX(R) B/E. All participants were given counseling on how to avoid getting HIV.
During the three-year study, participants were routinely tested for HIV. By the end, a total of 74 recipients who had received the placebo contracted HIV, while only 51 of the vaccine recipients contracted the virus. The results of the study indicate that the vaccine is 31.2 percent effective in preventing acquisition of HIV, the virus that causes AIDS.
Lt. Gen. Eric B. Schoomaker, the Army surgeon general, and commander of the U.S. Army Medical Command, said the results of the study are important, but modest.
"I'm pleased and proud to announce the results of the trial, which for the first time ever, have shown that it is possible for a vaccine to reduce the risk of HIV infection in humans," he said. "Although the level of protection is modest, at 31-percent efficacy, the study represents a major scientific achievement."
Schoomaker went on to say the Army's interest in the study is concurrent with its longstanding interest in protecting all servicemembers from infectious diseases.
"Military medicine is interested in research that improves global health and makes the world safer for everyone, including our Soldiers, Sailors, Airmen, Marines and Coast Guardsmen," he said. "The results of this trial opens new doors, answers some questions and poses many additional questions. This is truly a great moment for world medicine and for the global human family."
Col. Jerome Kim, an infectious disease expert, and the U.S. Army HIV Vaccine Product Manager at the Walter Reed Army Institute of Research, Division of Retrovirology, said researchers will now try to understand why the vaccine worked in some people.
"Additional studies are clearly needed to better understand how this vaccine regimen reduced the risk of HIV infection," he said. "The collaborators are meeting with outside experts to attempt to understand why the vaccine worked. The data derived from these analyses should drive the science and the discussions and hopefully allow us to move expeditiously to an effective preventative vaccine."
The combination of vaccines used during the RV144 study was shown to be effective against subtype B and subtype E of HIV, which are the most prevalent subtypes of the virus in Thailand. Kim said right now, researchers don't know if the combination of vaccines would have the same effect in other parts of the world, such as on the African continent, where other subtypes of the virus are prevalent.
"Whether this will work in other parts of the world with different subtypes of HIV or in populations at different risk of HIV infection, is not known," he said.
The study also showed that while some participants were prevented from contracting the virus, the vaccine did not have an effect on the severity of contracted HIV infections, said Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases.
"One of the most important and intriguing findings of the Thai trial, is that the vaccine regimen prevented HIV acquisition among a modest proportion of vaccinated participants, yet failed to affect viral load in vaccine recipients who later became infected," Fauci said. "This clearly begs the question of whether the protective immune responses that prevent infection are related to those that control viral load."
The three-year study was conducted as a partnership between the Army, the Thai Ministry of Public Health, the National Institute of Allergy and Infectious Diseases, Sanofi Pasteur, and Global Solutions for Infectious Diseases.