New HIV Vaccine Hails from Thailand

Prat Boonyawongvirot, Permanent Secretary of the Ministry of Public Health of Thailand, addresses a high-level meeting on HIV/AIDS at the United Nations in New York. Credit UN Photo/Devra Berkowitz

By Sue Gloor

A ground-breaking experiment in Thailand has led researchers to be optimistic about a vaccine to prevent HIV.

The experiment is the largest-ever HIV vaccine trial, and combined the administration of two HIV vaccines, both used previously with no results. The vaccines target the B and E strains of HIV since those strains are predominant in Thailand. The C strain, most prevalent in Africa, was not tested.

The subjects of this trial were 16,395 HIV-negative men and women from all over Thailand between the ages of 18 and 30. Half of the trial’s participants were given the vaccine, and half were given the placebo, after which they were all counseled in HIV prevention. Over the course of three years, the participants were tested for HIV every six months. The experiment resulted in a startling finding that has yet to be supported by additional trials, though it is promising just the same.

Of the subjects who received the placebo, 74 contracted HIV over the three-year period. Of the vaccinated participants, 51 became infected with HIV in the same period. This translates to a 31.2% decrease in HIV infection with the vaccine.

Though a direct causal relationship between the vaccine and diminished HIV infection has not been substantiated, the World Health Organization and the Joint United Nations Programme on HIV/AIDS hailed the study as successful.

Even Dr. Richard Horton, editor of the Lancet Medical Journal, stated that the findings “may have been due to chance,” and while they are encouraging, they cannot be relied on yet.

Studies of this nature are particularly difficult to employ, since some of the volunteers receive an un-tested vaccination comprised of a very harmful and serious virus. If the vaccine is not weak enough, it could potentially trigger the infection of HIV itself rather than prevent it.

However, the new experiment from Thailand seems to be on the right track.