From a statement by the National Institutes of Health:

The National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, has stopped administration of vaccinations in its HVTN 702 clinical trial of an investigational HIV vaccine. This action was taken because an independent data and safety monitoring board (DSMB) found during an interim review that the regimen did not prevent HIV. Importantly, the DSMB did not express any concern regarding participant safety.

The Phase 2b/3 study, named HVTN 702 or Uhambo, began in 2016 and is taking place in South Africa. It was testing an investigational prime-boost vaccine regimen based on the only vaccine regimen ever to show protection from HIV—the regimen tested in the RV144 clinical trial in Thailand led by the U.S. Military HIV Research Program and the Thai Ministry of Health. For HVTN 702, the vaccine regimen was adapted to the HIV subtype Clade C most common in southern Africa, where the pandemic is most pervasive.

“An HIV vaccine is essential to end the global pandemic, and we hoped this vaccine candidate would work. Regrettably, it does not,” said NIAID Director Anthony S. Fauci, M.D. “Research continues on other approaches to a safe and effective HIV vaccine, which I still believe can be achieved.”

Science Magazine reports:

“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 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.