The World Health Organization began large-scale testing of an experimental Ebola vaccine in Guinea on Saturday.
Dr. Marie-Paule Kieny, WHO assistant director-general, told The Associated Press that the agency intended to "vaccinate for this trial up to 10,000 people, maybe more."
"But also the manufacturers are producing much more vaccine right now, so that if the vaccine is proven to be efficacious, there could be millions of doses available later in the year," she said.
The vaccine was developed by the Canadian government about 10 years ago, but little more was done with it then because there was no demand for it at that time.
The health agency's vaccination strategy in Guinea aims to create a buffer zone around future Ebola cases to prevent its further spread.