A clinical trial for an HIV vaccine has been discontinued since the vaccine was not found to prevent infections of human immunodeficiency virus, the virus that causes AIDS. The National Institute of Allergy and Infectious Diseases or NIAID, which sponsored the trial, announced on Monday that the study taking place in South Africa was halted after an independent data and safety monitoring board found the vaccine to be ineffective in preventing HIV. The vaccine trial, named HVTN 702 or Uhambo, began in 2016 and enrolled 5,407 HIV-negative volunteers at 14 sites across South Africa, according to NIAID. Those volunteers were sexually active men and women ages 18 to 35 who were randomly assigned to receive either the vaccine or placebo injections. An analysis of the study showed no significant difference in subsequent HIV infections among the volunteers in the vaccine group versus placebo group.