Promising Vaccine may Help Prevent HIV Infection

Researchers have been working for years to develop a vaccine that would help bring the AIDS epidemic to a halt. There have been many failures recently, leading scientists to think that such a vaccine would never be a possibility. But now an experimental vaccine has actually prevented infection by the AIDS virus in a huge trial of people, and there is excitement and hope that scientists might have finally succeeded.

Researchers in Bangkok announced that in the world's largest trial of an AIDS vaccine to date, the vaccine lowered the risk of HIV infection by more than 31%. This most recent trial involved more than 16,000 volunteers in Thailand. The vaccine used is a combination of two vaccines that were previously unsuccessful. The test involved a "prime-boost" method, where the first vaccine kick-starts the immune system to attack the HIV, and the second one serves as a booster to strengthen the body's response. The first vaccine is ALVAC, created by the vaccine division of the French drugmaker Sanofi-Aventis. The second is ADISVAX, which was originally created by VaxGen but now held by a nonprofit group founded by former VaxGen employees, called Global Solutions for Infectious Diseases.

UNAIDS (a U.N. agency) and the World Health Organization have said that the results instill new hope for researchers working in the field of HIV vaccine development, although they say that it a vaccine will probably take many years to fully develop. Even though 31% is a modest benefit, scientists say that it is the first evidence that a safe and effective vaccine may one day be developed. Neither vaccine is made from whole HIV cells, so they cannot cause HIV in test subjects.

The study evaluated the combination of vaccines in 18- to 30-year-old HIV-negative men and women who had an average risk of becoming infected with the strains of HIV common to Thailand. Half of the study group were given four doses of the "priming" vaccine ALVAC and two doses of the "booster" drug AIDSVAX over the course of six months. The other half of the group was given placebo shots. None of the participants knew which group they belonged to until the study was over. All participants received condoms, counseling, and any treatment required for sexually transmitted diseases, and they were tested regularly for HIV. Anyone who tested positive was given free treatment, and all study participants continued receiving an HIV test for three years beyond the end of the study. Out of the two groups, 74 of the placebo group developed new infections, but only 51 of the vaccine group developed new infections, resulting in a 31% lower risk of infection for the group that received the vaccines.

The AIDS Vaccine Advocacy Coalition, which has worked diligently to develop a vaccine, said that the study results mark a historic milestone for researchers. Although it will require time and resources to analyze the data completely, the study findings will no doubt energize researchers and redirect their efforts toward developing a vaccine.

The study was led by the U.S. Army, co-sponsored by the National Institute of Allergy and Infectious Diseases. The institute's director, Dr. Anthony Fauci, told the media that although he was surprised and pleased by the successful outcome of the trial, this certainly does not signal the end of the road in AIDS vaccine research. "It gives me cautious optimism about the possibility of improving this result" and developing a more effective AIDS vaccine, Fauci said. "I really didn't have high hopes at all that we would see a positive result. But this is something that we can do."