HIV Vaccine Trial Shows Positive Gains Via Negative Results

The HIV vaccine that researchers gave to 16,000 adult volunteers was 31 percent effective in preventing HIV infection, according to the Thai Ministry of Public Health.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, which provided additional funding and support for the study, called it an "important step forward in HIV vaccine research" in a statement, but emphasized "additional research is needed to better understand how this vaccine regimen reduced the risk of HIV infection."

The protection provided by the vaccine is far too low for distribution, said Dr. Alan Bernstein, executive director of the Global HIV Vaccine Enterprise, so the trial was not a home run, but as the results are analyzed it should provide cues as to where to focus efforts next.

Failed attempts before

	While there is no AIDS vaccine, patients can take anti-retroviral drugs to treat the disease.

These trial results are a major boost for the HIV vaccine field, which suffered a crushing blow in late 2007 with the failure of a promising Merck vaccine that actually raised the risk of HIV infection for some participants.

After the Merck trial was shut down, many in the field felt they were at a dead end, "I think the field went into a funk, a feeling that we really don't know what direction to go," said Bernstein, who was happily surprised by the positive results of the Thai trial.

"My heart skipped a beat," he said. "This is really a landmark day, a momentous day, not just for the field, but for the planet."

"No one could have predicted accurately the results that we heard about today," continued to Bernstein, "So it's a demonstration that we have a lot to learn still about how we protect ourselves from HIV."

HIV hard to vaccinate

	AIDS is caused by the HIV virus (above in red) which attacks white blood cells in the body's immune system.

Particularly surprising to researchers and experts is the vaccine in this trial prevented infections, but didn't reduce overall viral load in the participants.

The assumption, said Rowena Johnston, vice president of research for the Foundation for AIDS Research, has always been that it would be easier to develop a vaccine that had a therapeutic effect, but the shot failed to reduce the amount of virus in the blood of people already infected.

Researchers had hoped that if the vaccine didn't prevent infections, it would at least cut the virus to levels so low it couldn't be transmitted.

"It seemed like a lower bar to modify infection after it occurs as opposed to actually preventing infection in the first place," said Johnston, but the trial results suggest the opposite.

Johnston said that when the blood samples are analyzed further, researchers will be able to compare the immune response of a vaccinated individual who still became infected to the response in a vaccinated individual who was protected, providing a sign post for future research that has never been available before.

Vaccine could make a difference in millions of lives

	As of 2007, an estimated 32.9 million people were living with HIV/AIDS worldwide according to UNAIDS.

The Thai study opened in October 2003 and tested a two-vaccine combination in a "prime-boost" approach, in which the first one primes the immune system to attack HIV and the second one strengthens the response.

Neither vaccine used in the study stopped HIV infection when tested alone in previous trials, raising some questions about if the combined trial should be done.

The first vaccine used an altered bird virus to carry synthetic version of three HIV genes into the body.

The second contained a genetically engineered version of a protein on HIV's surface. Both vaccines used individual components of the virus that cannot cause an HIV infection.

Participants were counseled on how to avoid becoming infected with HIV and were tested for HIV infection every 6 months for 3 years.

In the final analysis, 74 of 8,198 placebo recipients became infected with HIV compared with 51 of 8,197 participants who received the vaccine regimen.

The level of prevention, 31 percent, did not come near the 80 percent level necessary to be licensed, Johnston said, but if an HIV vaccine with that level of protection can eventually be developed, she said it would "make a meaningful difference in millions of people's lives."