a94d1cea-49b2-48e4-95cf-0c609a8a6953_fullhd.mp4 video player.

South Sudan is vaccinating health workers against Ebola in case the virus crosses the border from the Democratic Republic of Congo. Ebola has stricken more than 700 people in the DRC and killed more than 400. The World Health Organization said the death rate is 59 percent. 

Half a world away in Ohio, U.S. researchers are racing to develop a new, long-lasting vaccine against Ebola. At Cincinnati Children's Hospital Medical Center, Dr. Paul Spearman is leading a clinical trial that tests two experimental Ebola vaccines.

"Researchers are looking for new ways to stop these outbreaks and to treat people who become infected and develop Ebola virus disease. The development of preventive vaccines for Ebola is a top global public health priority," said Spearman, director of the Division of Infectious Diseases at Cincinnati Children's and the lead investigator in the trial.

FILE - A Congolese health worker administers Ebola
FILE - A Congolese health worker administers Ebola vaccine to a woman who had contact with an Ebola sufferer in the Democratic Republic of Congo, Aug. 18, 2018.

Volunteers first receive one of the vaccines. A week later, they get the other one. Spearman said this one-two shot is promising and could provide rapid protection against Ebola.

These are weakened live-vector vaccines that cannot grow in human cells, but they produce strong immune responses to Ebola virus proteins.

Karnail Singh, Ph.D., also at Cincinnati Children's, heads the program that tests volunteers' blood samples. The researchers test the samples collected before the volunteers are injected with the experimental vaccines and again afterward.

Singh said that way, researchers can compare the samples and see if the vaccines provide immunity. The researchers also plan to take blood samples six months after the first two injections. If the vaccine is still effective, they hope to repeat the process six months later. These intensive lab studies and the rapid prime-boost schedule have not been done before in developing a vaccine against Ebola.

In Congo, health workers are using a vaccine developed during the Ebola outbreak in West Africa that raged from 2013 until 2016. It protects the Zaire strain of Ebola circulating in Congo. But there are two other deadly strains of Ebola. Health officials want vaccines that protect against all of them. 

The vaccine being tested at Cincinnati Children's has not yet been compared to the one being used in Congo, but it may protect against at least one other strain of Ebola. The goal is to produce a vaccine that is safe, effective and long-lasting.

The researchers in Cincinnati hope their work will improve the understanding of how to build immunity to other viruses or bacteria that can cause disease.