The latest news on HIV from Thailand indicates that the HIV vaccine is effective in only 31 percent of individuals. This phase lll clinical trial involving more than 16,000 adult volunteers did demonstrate that the vaccine was safe but its effectiveness was not as expected.
Based on the final results by the trial sponsor, the U.S. Army Surgeon General, the prime boost combination of ALVAC® HIV and AIDSVAX® B/E only decreased the rate of HIV infection by 31.2% compared with placebo. Of those who received the vaccine, 51 contracted HIV, while 74 in the placebo group got infected — a difference of 23 people. Not a big difference by any means.
Analysis of the data using other statistical methods suggests that the vaccine’s perceptible minor effectiveness against HIV, could have been simply been due to statistical chance. Still, there are other research scientists who claim that the Thai study was clinically useful because it was the first large-scale HIV-vaccine trial to capitulate an affirmative result.
“The results are qualitatively similar along all three analyses,” said Seth Berkley, president and chief executive of the International AIDS Vaccine Initiative, who was at the Paris meeting. “Most of the skeptics would say that there’s a signal there” that indicates an immune response.
Discovering what triggers the immune response to HIV is key to future development of any vaccine. With HIV, researchers would like to know whether the obvious immune response is associated to antibodies or T-cells, the chief target of HIV in blood. But so far, finding the right trigger(s) has been exceedingly difficult.
Several years ago, Dennis Burton of Scripps Research Institute in La Jolla, Calif., and several other researchers openly inquired about benefits of the Thai study. These scientists did indicate that the vaccine tested by the Thai researchers combined a failed vaccine and was deemed to have a very minimal chance of success.
“It has some, although albeit modest, results, some very encouraging results that can be used to guide further efforts in vaccine development,” Maureen Birmingham of the World Health Organization said.
Since the trial was conducted in Thailand, it is not known how individuals in other parts of the world may respond because there are different strains of HIV. Finally, the Thai trial included individuals from the general population and did not include a high risk group. Therefore, it is not known whether the vaccine would have shown a similar benefit in gay men, drug users or prostitutes who have a high risk of acquiring HIV.
