The National Institutes of Health has started human trials of a second experimental Ebola vaccine. The agency announced it is testing VSZ-ZEBOV in healthy adults using a prime-boost strategy, which means volunteers receive two doses of the injection. The Walter Reed Army Hospital’s Institute of Research is also testing the vaccine as a single dose.

Canada’s National Microbiology Laboratory developed the vaccine, which has been licensed to NewLink Genetics Corp. It is now the second Ebola vaccine the NIH has used in human test subjects — it started testing an experimental GlaxoSmithKline vaccine in humans in September.