Jan. 23, 2015 --The first shipment of an experimental Ebola vaccine is being sent to Liberia for field testing, but experts say it may be difficult to determine how effective it is because the number of Ebola cases in West Africa is falling.
An airplane carrying about 300 initial doses of the vaccine made by GlaxoSmithKline (GSK) and the U.S. National Institutes of Health (NIH) is expected to arrive in Liberia on Friday, and a clinical trial of the vaccine could begin within a few weeks, BBC News reported.
Researchers plan to give the vaccine to 10,000 volunteers and another 10,000 will receive a placebo. Another 10,000 people will get a different experimental vaccine.
The GSK-NIH vaccine was previously tested on 200 healthy people in the U.S., U,K., Mali and Switzerland and was found to be safe. However, tests in countries affected by Ebola are the only way to determine if the vaccine provides sufficient protection against the deadly virus, BBC News reported.
But it may be difficult to assess the true effectiveness of the vaccine with the number of Ebola cases declining, according to an expert.
"Because case numbers are starting to come down it will become harder and harder to show if the vaccine is having any impact," Professor Jonathan Ball, a virus expert at Nottingham University in the U.K., told BBC News.
"Ultimately we may be in position in a few months time where we don't know whether this vaccine is effective in humans," he added. "But it is important to get answers if we can -- if not for this outbreak, for future outbreaks. We need to be prepared."
Clinical trials of other experimental Ebola vaccines are planned in Guinea, Liberia and Sierra Leone in the coming months, while the trial of an experimental drug called Zmapp might begin in the next few weeks, BBC News reported.