Swiss regulators announced they would allow trials of an experimental vaccine made by Britain's GlaxoSmithKine, and tests on some 120 individuals were set to get under way at the CHUV hospital in Lausanne Friday, the hospital said.
"We have never before received so many volunteers so quickly," Blaise Genton, who heads CHUV's infectious disease division, told reporters.
He said the volunteers, who must be between the ages of 18 and 65, were mainly medical students and would all receive 800 Swiss francs (USD 845, 665 euros) for their participation.
Most of the volunteers will receive the experimental GSK vaccine called ChAd3, which is based on a genetically modified chimpanzee adenovirus, but 20 of them would receive a placebo he said.
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WHO hailed the announcement.
"This marks the latest step towards bringing safe and effective Ebola vaccines for testing and implementation as quickly as possible," the UN's health agency said in a statement.
There is no licensed treatment or vaccine for the deadly Ebola virus, which has killed nearly 5,000 people in the outbreak centred in west Africa.
"The trial will test the safety of the vaccine and its capacity to induce an immune response," WHO said.
It added that results of the trials in Switzerland and elsewhere will "provide the basis for planning subsequent trials involving several thousand participants, and for choosing vaccine dose-level for efficacy trials."
A second experimental vaccine being fast-tracked on the WHO's recommendation, Canadian-discovered rVSV, is set to soon start trials at the University Hospital of Geneva.
Trials of that potential vaccine have already begun in the United States and are also set to soon start in Germany, Gabon and Kenya.