HIV Vaccine Shows Promise In Trial

Main Category: HIV / AIDS
Also Included In: Immune System / Vaccines
Article Date: 25 Sep 2009 - 3:00 PDT

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A U.S.-backed vaccine experiment in Thailand has for the first time demonstrated a "small but measurable" benefit in preventing HIV infection, the Washington Post reports (Brown, Washington Post, 9/24). Col. Jerome Kim, a physician involved with the trial who is manager of the army's HIV vaccine program, said that although the reduction in transmission was small, it is statistically significant and means the vaccine was 31.2% effective (McNeil, New York Times, 9/25). According to the Post, the "chief usefulness" of the vaccine is "likely to be what it can teach virologists about what is happening in the immune system when a person is even somewhat protected from HIV." The vaccine is not expected to be licensed or produced in large amounts, and it is unlikely that countries would consider it effective enough to be used as a public health measure to reduce the spread of HIV. Nonetheless, the findings are considered a milestone, as they mark the first positive results of an HIV vaccine after two decades of experiments (Washington Post, 9/24).

The vaccine combines Sanofi-Pasteur's ALVAC canary pox vaccine and AIDSVAX, a failed HIV vaccine made by VaxGen, which is owned by the not-for-profit Global Solutions for Infectious Diseases (Fox, Reuters, 9/24). The six-year study involved 16,000 Thai men and women and was run by the U.S. Army, NIH and Thailand's Ministry of Public Health. According to the Post, about 40% of the participants were women, and many were employed in shipping and manufacturing enterprises along the Thai coast. A few were injection drug users and men who have sex with men -- two groups considered at high risk for HIV transmission. Researchers randomly assigned participants to receive the vaccine or a placebo. Participants were counseled on methods of HIV prevention and advised to use condoms (Washington Post, 9/24).

The participants received six immunizations over six months, two with AIDSVAX and four with ALVAC (Reuters, 9/24). Fifty-one of the 8,197 vaccinated people became infected with HIV in the three years after the shots, compared with 74 of the 8,198 people who received placebos (Washington Post, 9/24). Further details of the study, which cost $105 million, will be presented at a vaccine conference in Paris in October (Marchione, AP/San Francisco Chronicle, 9/24).

Researchers said the vaccine, known as RV 144, "protected too few people to be declared an unqualified success," and they were also "puzzled" by the trial's results because the vaccine did not change the amount of HIV in a person's blood compared with someone who received a placebo, the New York Times reports. A vaccine that offers partial protection typically lowers the viral load. However, this did not occur in the trial, which suggests that the vaccine does not produce neutralizing antibodies -- which attack virus cells -- like most vaccines, according to Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, which paid for most of the trial. He said the vaccine may produce "binding antibodies," which attach themselves to and empower effector cells, a type of white blood cell attacking the virus (McNeil, New York Times, 9/25).

Fauci said, "Conceptually, we know a vaccine is possible," adding, "Whether the vaccine is going to look anything like this one, I don't know. But at least we know it can be done" (Washington Post, 9/24). Mitchell Warren, executive director of AVAC, the AIDS Vaccine Advocacy Coalition, said that the results of the study are "hugely exciting and, frankly, unexpected," adding that although RV 144 "is not the vaccine that ends the epidemic," it is "a fabulous new step that takes us in a new direction" (New York Times, 9/25).

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