Tens of thousands of people in West Africa are expected to begin getting experimental Ebola vaccines from January, but population-wide immunization is still far off, the World Health Organization (WHO) said on Tuesday.

Initial clinical trials of vaccines from GlaxoSmithKline and NewLink Genetics are already under way. Some 500 volunteers are due to take part in countries including the United States, Britain, Germany, Switzerland, Mali, Gabon and Kenya.

The tests will generate safety and immune-response data in December. The vaccines can then be rolled out early next year to groups including frontline healthcare workers, said Marie-Paule Kieny, the WHO assistant director-general for health systems and innovation.

"These data are absolutely crucial to allow decision-making on what dose level should go into efficacy testing in Africa," Kieny told a news briefing.

Determining the dosage will dictate the yield or overall amount of vaccine available for the large clinical trials in Africa, she said.

"There is still a possibility that it will fail, but everybody is putting things in order in order for being able to move to West Africa in January," Kieny said. "When I say deployed, I am not talking about mass vaccination, I am talking about utilization in the tens of thousands of doses in the first couple of months of the year."

West Africa's Ebola outbreak, which began in March, has killed 4,546 out of 9,191 known cases in Guinea, Liberia and Sierra Leone, according to WHO, which has declared outbreaks in Senegal and Nigeria over.

There have been a handful of Ebola cases in Spain and the United States, which on Monday issued stringent new protocols for health workers treating Ebola victims.

FUNDING THE ROLL-OUT

Vaccine makers and regulatory authorities are moving quickly to speed up trials and approval for the vaccines, Kieny said. Donors stand ready to help finance the roll-out, expected to cost hundreds of millions of dollars, she added.

"The funding scenario has not been worked out. But what we are working on for the time being is the assumption that the funding will come from the countries who are helping with the response, so indeed the U.S., UK, France, Norway, Germany and many others as well as from the GAVI," she said.

The Geneva-based GAVI alliance procures vaccines at affordable prices for use in developing countries.

While the GSK and the NewLink vaccines, the latter developed by Canada's Public Health Agency and licensed to the U.S. firm, are considered "lead candidates", others are being developed.

Johnson & Johnson has a candidate vaccine that is expected to start clinical trials in January, Kieny said.

Inovio Pharmaceuticals is developing a DNA vaccine that would enter clinical tests early next year. Protein Sciences is developing a vaccine that should reach trials in the first quarter of 2015, she said. Both are U.S.-based companies.

Russia has been developing Ebola vaccines, but their status is less clear, Kieny said.

"The best that I know is that one of the vaccines is either currently or has already been in clinical trials, in Phase I clinical trials, to assess safety and immunogenicity in Russia," she said. "We are currently discussing with them to know a bit more about what are the results and what are their plans."

Experimental drugs against Ebola include Fujifilm's flu drug Avigan, or favipiravir, the safety and efficacy of which the French government will evaluate in a clinical trial in Guinea, she said. The trials are expected to start in coming weeks, she said.

Asked whether this would be the first drug used in trials in Ebola-affected West African countries, Kieny said: "If it starts on time, as far as I am aware, yes."

British scientists said on Tuesday that Avigan might also have potential against norovirus, or the winter vomiting bug.

The U.S.-made drug ZMapp from Mapp Biopharmaceutical has been given to a handful of infected health workers evacuated from the region, but this has been on an ad hoc basis, she said.