On Monday, Liberia began the first large-scale trials of two experimental Ebola vaccines. Scientists in Liberia plan to immunize 30,000 volunteers and healthcare workers with the new drugs.
The trial that began on Monday included injecting the volunteers with a strain of the Ebola virus to trick their bodies into developing immune responses. But scientists aren't sure whether the trial vaccines will be effective against Ebola. Monday's test involves 12 volunteers, and more volunteers will be given the vaccine as the trial continues.
More than 8,500 people have died in the Ebola outbreak, including 3,600 in Liberia alone. If successful, the new trials may reveal the first preventive vaccine against the disease.