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Data from an AIDS vaccine trial in Thailand is confirming the prototype as only a partial shield against HIV, but still a pioneering achievement.
Volunteers who received the vaccine had a 31.2-% reduction in the risk of infection by the human immunodeficiency virus (HIV), Thai and US researchers told an international conference.
It marks the first piece of solid good news in the quest for a vaccine against AIDS, which has claimed more than 25 million lives since 1981 and left some 33 million people infected, a tally rising by around 7,400 new cases per day.
The researchers cautioned that the vaccine was still far from the mark -- generally considered to be at least 50% protection -- by which it could be distributed to the public.
But, they said, it was an important morale-booster, proving that there were ways to prime the immune defences against a stealthy foe.
The study was published simultaneously in the peer-reviewed New England Journal of Medicine as Michael and his Thai counterpart, Superchai Rerks-Ngarm, made their presentation at the AIDS Vaccine 2009 conference in Paris.
The study recruited 16,395 HIV-negative volunteers, of which 8,197 received the vaccine while the 8,198 others received a harmless lookalike called a placebo. The vaccine is in fact a combination of two vaccines, ALVAC and AIDSVAX, that were designed some 15 years ago and, in separate trials, had previously been found to be safe but of negligible
effectiveness.
The conclusion of 31.2-percent effectiveness derives from the number of people who became infected: 51 in the vaccinated group, against 74 in the placebo group. The researchers acknowledged that the number of infections overall was low, but said the outcome was still statistically significant.
