US and Thai Governments Defend HIV/AIDS Vaccine Trial in Thailand

Article excerpt

Public health officials and scientists from the US and Thai Governments have countered accusations by a group of HIV/AIDS researchers who questioned the scientific rationale behind a Thai and US Government-backed trial of an HIV/AIDS vaccine in Thailand.

The phase III trial is testing a vaccine combination that critics say has no "reasonable prospect" of protecting anyone. In an article in Science magazine (2004;303:316), 22 HIV researchers contend that scientific evidence for the vaccine is "extremely weak," and they "doubt whether these immunogens have any prospect of stimulating immune responses anywhere near adequate for these purposes." They also argue that any new scientific knowledge that the trial might produce is not worth the US$ 119 million cost and effort.

However, in a rebuttal published in Science (2004;303:961), John McNeil and other scientific officers from the sponsoring agencies argue that the decision to proceed with the trial is "scientifically justified, morally correct and strategically important." In the same issue of Science (2004;303:954-5), Charal Trinvuthipong, Director General of the Department of Disease Control in Thailand's Ministry of Public Health which is co-sponsoring the trial, pointed out that the critics' argument was flawed and that "there is no such thing as wasting time or money in researching an AIDS vaccine."

In September 2003, the first of 16 000 young, heterosexual volunteers began receiving the vaccine which comprises Aventis-Pasteur's live canarypox virus vector ALVAC combined with VaxGens genetically engineered HIV surface protein gp120. The Aventis-Pasteur vaccine is designed to stimulate cellular immunity by promoting the growth of cytotoxic T cells. VaxGen's gp120 vaccine aims to induce antibodies against HIV. According to the critics, phase I and 11 clinical trials revealed that the ALVAC vector alone was poorly immunogenic, and trials in the US and Thailand indicated that the gp120 component was completely incapable of preventing or ameliorating HIV-1 infection." The "prime-boost" combination vaccine was designed to strengthen cellular and humoral immunity to prevent and or control HIV-1 more than either vaccine does alone.

The critics argue that "there are no persuasive data" to support this idea. "I don't think there's anyone who thinks this will be protective," said Beatrice Hahn of the University of Alabama in the US, a co-author of the critique in Science. For a phase III trial to be justifiable, there should be a "reasonable prospect" that the vaccine will benefit the study population but this prospect is lacking, argue the authors.

The article accuses the National Institutes of Health (NIH), the agency of the US Department of Health and Human Services backing the trial, of not consulting closely enough with independent experts. …