Dr Ripley Ballou, GSK: “It normally takes 7 to 10 years to develop a vaccine.”
UK pharmaceuticals firm GlaxoSmithKline says its Ebola vaccine will “come too late” for the current epidemic.
GSK is one of several companies trying to fast-track a vaccine to prevent the spread of Ebola in West Africa.
But Dr Ripley Ballou, head of GSK’s Ebola vaccine research, said full data on its safety and efficacy would not be ready until late 2015.
The World Health Organization (WHO) says more than 9,000 people have been infected and more than 4,500 have died.
Health workers are struggling to contain the spread of the virus, which is mostly affecting people in Liberia, Guinea and Sierra Leone.
The WHO has warned there could soon be 10,000 new cases a week.