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A trial in South Africa was halted after early analysis found no protection. The failure-ridden search for a vaccine that can stop the AIDS virus has delivered yet another frustrating defeat. The HIV vaccine that had moved furthest along in human testing does not work, and the $104 million trial in South Africa evaluating it has been stopped early. “There’s absolutely no evidence of efficacy,” says Glenda Gray, who heads the study and is president of the South African Medical Research Council (MRC). “Years of work went into this. It’s a huge disappointment.”
The efficacy study, which began in October 2016, is known as HVTN 702. It enrolled 5407 sexually active, HIV-uninfected men and women between 18 and 35 years of age at 14 sites across the country. Researchers randomly assigned half of the participants to receive a pair of HIV vaccines used in a one-two punch called a prime boost, whereas the other half received placebo shots. The trial was supposed to last until July 2022. But on 23 January, an independent monitoring board that takes scheduled, sneak peaks at the data to evaluate safety and efficacy, informed Gray and the other leaders of the study that it was “futile” to continue. There were 129 infections in the vaccinated group and 123 in those who received the placebo. “I was catatonic,” Gray says. No evidence exists that the vaccine caused harm, as happened in a different large HIV vaccine study that was abruptly halted in 2007. Susan Buchbinder, an epidemiologist at the University of California, San Francisco, who co-chaired that earlier sobering study, congratulates her colleagues in South Africa for conducting a scientifically rigorous, complex trial. “The trial was incredibly well done and we got a definitive answer, and that’s what science is about,” says Buchbinder, who is the chair of a multicountry trial, Mosaico, that now is the most advanced large-scale HIV vaccine study underway.
In the halted trial, funded by MRC, the U.S. National Institute of Allergy and Infectious Diseases (NIAID), and the Bill & Melinda Gates Foundation, the “prime” was a harmless canarypox virus that carries genes for HIV’s surface protein and two of its other structural proteins. The boost contained a recombinant version of the surface protein mixed with an immune system booster, or adjuvant, called MF59. Many HIV scientists had doubted the South Africa study would succeed because the vaccines used in the prime-boost scheme had only produced lackluster results in an efficacy study in Thailand. In that study, which ended in 2009, HIV infections totaled 51 in the vaccine group and 74 in the placebo arm—an efficacy of 31%. The field widely agreed that this wasn’t a high enough level of protection to bring the vaccine to market, but researchers were divided as to whether it made sense to try to build on the vaccine or abandon it.....
