"Scientists researching the lethal Ebola virus have told [BBC News] that a commercial vaccine to prevent the onset of infection may never be developed," the news service reports. "Efforts to develop a vaccine have been funded in the main by the U.S. Department of Defense and the National Institutes of Health," which "have poured millions of dollars into scientific research because of concerns that the virus could be turned into a biological weapon," the news service writes. But in recent days, two companies that had begun human safety trials of their vaccines, Sarepta and Tekmira, "have been told by the Defense Department to temporarily stop work on their vaccines due to funding constraints."