For the first time, an AIDS vaccine has shown some success in trials:
Results of the trial of the vaccine, known as RV 144, were released at 2 a.m. Eastern time Thursday in Thailand by the partners that ran the trial, by far the largest of an AIDS vaccine: the United States Army, the Thai Ministry of Public Health, Dr. Fauci’s institute, and the patent-holders in the two parts of the vaccine, Sanofi-Pasteur and Global Solutions for Infectious Diseases.Col. Jerome H. Kim, a physician who is manager of the army’s H.I.V. vaccine program, said half the 16,402 volunteers were given six doses of two vaccines in 2006 and half were given placebos. They then got regular tests for the AIDS virus for three years. Of those who got placebos, 74 became infected, while only 51 of those who got the vaccines did.
Although the difference was small, Dr. Kim said it was statistically significant and meant the vaccine was 31.2 percent effective.
Dr. Fauci said that scientists would seldom consider licensing a vaccine less than 70 or 80 percent effective, but he added, “If you have a product that’s even a little bit protective, you want to look at the blood samples and figure out what particular response was effective and direct research from there.”
The most confusing aspect of the trial, Dr. Kim said, was that everyone who did become infected developed roughly the same amount of virus in their blood whether they got the vaccine or a placebo.
Normally, any vaccine that gives only partial protection — a mismatched flu shot, for example — at least lowers the viral load.
That suggests that RV 144 does not produce neutralizing antibodies, as most vaccines do, Dr. Fauci said. Antibodies are long Y-shaped proteins formed by the body that clump onto invading viruses, blocking the surface spikes with which they attach to cells and flagging them for destruction.
Instead, he theorized, it might produce “binding antibodies,” which latch onto and empower effector cells, a type of white blood cell attacking the virus.
Whatever the vaccine does, he said, it does not seem to mimic the defenses of the rare individuals known to AIDS doctors as “long-term nonprogressors,” who do not get sick even though they are infected. They have low viral loads because they block reproduction in some way that is still mysterious.