AIDS: an experimental vaccine "modest" but gives hopes

The "modest" results in a vaccine trial conducted in Thailand are still leading the way in research, even if the vaccine against the AIDS virus not right around the corner," said researchers.

On 24 September, Thai and U.S. researchers have announced that the combination of two vaccines, ineffective individually, reduced the risk of infection with the AIDS virus by 31.2%.

The trial was conducted in Thailand with a population of over 16,000 people at average or low risk. The half had received the vaccine and the other a placebo. 125 people were infected, including 51 among vaccine recipients and 74 among those who received placebo.

It was the first time a vaccine gave favorable results. The AIDS epidemic affects over 25 million people. So far it infects 7400 more each day.

Detailed results of these tests were presented for the first time to the scientific community at the international conference "Aids Vaccine 2009", organized by the National Agency for AIDS Research (ANRS) and the Global HIV Vaccine Enterprise .

The researchers explained that the figure sometimes was disputed in the scientific community. 31.2% was based on "modified intent to treat", that is to say all persons got treatment, including those who had become infected before receiving all injections of vaccine.

The researchers admitted that results were "modest", even if they were "statistically significant". They also indicated that the effectiveness of the vaccine wanings over time. What would be effective in the long term? "I do not know," said Colonel Michael Nelson, the U.S. military program of research on the virus, co-sponsor of the study with the Thai government.

In addition, this vaccine has been developed to meet the type of virus circulating in Thailand and it is unclear whether it could be used elsewhere on the high-risk populations, such as Africa.

Finally the researchers noted that the vaccine did not offer very strong immune response and did not reduce the infection rate among the infected.

"This is definitely not a breakthrough for public health," said Michael Nelson, for whom the vaccine is far from "being right around the corner." But "it's a breakthrough for research."

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