Thailand: AIDS vaccine trial brings scientific breakthrough

Updated On: Sep 28, 2009

The world's largest HIV/Aids vaccine trial – jointly conducted in Thailand by the US military and Thai scientists over the last several years – has reported 31.2 per cent efficiency in reducing the risk of infection, although it failed to reduce the HIV virus in the blood of infected persons.

"The outcome represents a breakthrough in HIV vaccine development because for the first time ever there is evidence that an HIV vaccine can be effective," said Thailand's Public Health Minister Witthaya Kaewparadai.

Dr. Suppachai Rerk Ngam, project director for Thailand's Phase III HIV vaccine clinical trial, said researchers had aimed to achieve a 50 per cent efficacy rate. Although the results are modest and need further study, the trial has been hailed as a major scientific breakthrough by the medical world because it is the first time a vaccine has been shown to be able to prevent HIV infection.

The Thai experiment, known as RV 144, tested the "prime - boost" combination of two vaccines: ALVAC HIV vaccine (the prime) produced by SanofiPasteur, and AIDSVAX B/E vaccine (the boost) produced by the Global Solutions for Infectious Diseases. The “prime – boost” approach  combines two vaccines - the first one primes the immune system to attack HIV and the second one strengthens the response.

This combination was based on an HIV strain that commonly circulates in Thailand.

The RV 144 was designed to test the vaccine strategy's ability to prevent HIV infection, as well as its ability to reduce the amount of HIV in the blood (viral load) of those who became infected after they enrolled in the study.

The Public Health Ministry conducted the study, which was sponsored by the US Army Surgeon General with US$105 million (3.5 billion baht), while Mahidol University and the Armed Forced Research Institute of Medical Science, operating out of Thailand, helped to conduct the trial.

The Phase III vaccine study was launched in 2003 and involved 16,402 non-infected volunteers aged between 18 - 30 years, at average risk of HIV infection. Half of them received the vaccine combination and the other half received a placebo.


Asia One, Thailand's Aids vaccine trial shows positive results, 25 Sept 2009, http://health.asiaone.com/Health/News/Story/A1Story20090925-169838.html

BBC News, Thailand's long battle with HIV/Aids, 24 Sept 2009, http://news.bbc.co.uk/2/hi/asia-pacific/8273486.stm

AP, Volunteers key to success of Thai vaccine trials, 28 Sept 2009, http://www.google.com/hostednews/ap/article/ALeqM5hk604Cj2hHBoTBiGwRiJls...

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