WASHINGTON, Sept 24 (Reuters) - For the first time ever, an AIDS vaccine protected people from infection with the human immunodeficency virus, lowering the risk of infection by about 30 percent over three years. Here are some questions and answers about the study and AIDS vaccines: WHAT IS THIS VACCINE? The vaccine is not new but is a combination of Sanofi-Pasteur's <SASY.PA> ALVAC canarypox/HIV vaccine, which has synthetic versions of three HIV genes spliced into it, and the failed HIV vaccine AIDSVAX, made by a San Francisco company called VaxGen and now owned by the nonprofit Global Solutions for Infectious Diseases.AIDSVAX is made using two versions of one HIV gene, one from the B subtype or clade common in Europe and North America, and one from the E clade, common in Thailand. HOW DOES THE VACCINE WORK? Researchers are not sure. AIDS experts have long agreed that any HIV vaccine would have to activate both arms of the immune system -- the antibodies that home in on invaders such as viruses to neutralize them, and the T-cells that recognize and destroy viruses. This vaccine did not appear to generate either response, and yet prevented infection 30 percent of the time. Even more confusing, among the 51 people who were vaccinated but were infected anyway, the virus replicated just as well as it did among unvaccinated HIV patients. Researchers would not have expected that -- they would have expected the vaccine to at least make the infection less serious, as influenza vaccines do, for example. "Additional studies are clearly needed to understand how this vaccine regimen reduced the risk of HIV infection," said Dr. Jerome Kim of the Walter Reed Army Institute of Research in Maryland, who helped lead the study. WHY IS IT SO HARD TO MAKE AN AIDS VACCINE? Vaccinating against some agents is fairly easy. Polio vaccines use a weakened or killed version of the virus to prime the immune system, and smallpox was wiped out using a related, milder virus called vaccinia. But HIV is different. It is considered too dangerous to use the whole virus to prime the immune system and the virus infects the very immune system cells that normally are activated by a vaccine or by infection. In addition, HIV can sneak into cells and hide in them for years, so any vaccine would have to give people lifelong immunity -- because they would be at constant risk of infection from within. WHO WAS IN THE TRIAL? The trial was organized by the Thai government and military, who recruited 16,000 ordinary people considered at "community risk" of getting HIV. "What we mean by community risk is that we would include everyone in the community," Kim said. That includes a few commercial sex workers, men who have sex with men and perhaps injecting drug users -- all of whom would be considered at high risk of HIV. But many ordinary people at no extra risk also took part. The researchers will be keen to find out if this or a similar vaccine will work among people most likely to contract the virus, especially in Africa, where it is mostly transmitted between men and women. Two-thirds of all people infected with HIV live in sub-Saharan Africa and 75 percent of those who died from AIDS in 2007 were Africans. HOW MUCH DID IT COST? The trial cost $105 million and was mostly paid for by the U.S. National Institute of Allergy and Infectious Diseases, one of the National Institutes of Health. The U.S. Army paid for 25 percent of it. "It came in 15 percent under budget," said U.S. Army Surgeon General Dr. Eric Schoomaker. WHO CONDUCTED THE TRIAL? Thailand's Ministry of Health ran the trial, the largest ever HIV vaccine study. "They did a remarkable job of recruiting volunteers and conducting this trial almost flawlessly," Schoomaker said. WHO WILL MAKE THE VACCINE? Sanofi-Pasteur and Global Solutions for Infectious Diseases will work out details of potentially producing more vaccine to test and are currently consulting on how best to use remaining supplies of the vaccine. The trial was not designed to win U.S. Food and Drug Administration approval to license the vaccine. ARE THERE OTHER AIDS VACCINES Dozens of vaccines are in trials. The International AIDS Vaccine Initiative says 18 other trials are now ongoing at the phase II or III level, meaning vaccines are being tested in people to see if they might work even a little bit. Non-profit groups such as IAVI, as well as the U.S. government, are funding some of the trials and drug companies are funding others. WHY DO WE EVEN NEED AN AIDS VACCINE AIDS has killed 25 million people since the virus was first identified in the early 1980s. It infects an estimated 33 million people, according to the World Health Organization. There is no cure and while cocktails of drugs can control the virus, most people eventually develop what is known as resistance and have to switch to new drugs to stay healthy. IAVI estimates that a vaccine that prevented just 50 percent of cases given to 30 percent of the population would avert 5.6 million new infections in low and middle income countries between 2015 and 2030. Most people who are infected live in Africa and now most of these are women, many who are infected by their husbands or partners in a committed relationship. Many babies are also infected at birth and if HIV is in the population, people are at risk of getting it. The virus is transmitted in blood, breast milk, semen, on used needles and through sexual intercourse. (Editing by Todd Eastham)
Chief Executive Officer of Chris Veihbacher of French drugs group Sanofi Aventis speaks during a news conference in Paris, September 24, 2009. Sanofi announced the results of the collaborative AIDS vaccine ...
