GENEVA (AP) — Tens of thousands of doses of experimental Ebola vaccines could be available for "real-world" testing in West Africa as soon as January as long as they are deemed safe, a top World Health Organization official said Tuesday.

Dr Marie Paule Kieny, an assistant director general for WHO, said clinical trials that are either underway or planned in Europe, Africa and the U.S. are expected to produce preliminary safety data on two vaccines by December.

If the vaccines are declared safe, she said they will be used in trials in West Africa beginning in January to test their effectiveness among tens of thousands — but not millions — of people.

"I'm not suggesting at this moment that there would be mass vaccination campaigns at population levels starting in 2015," she said, adding that none of the volunteers who take part in the trials could accidentally contract Ebola from the testing.

The Ebola outbreak in West Africa has already killed over 4,500 people, mostly in Liberia, Guinea and Sierra Leone, since it emerged 10 months ago. Experts have said the world could face 10,000 new cases a week in two months if authorities don't take stronger steps to fight the deadly virus.

In Sierra Leone, the government said Tuesday that number of infected people in the country's western region is soaring, with more than 20 Ebola deaths a day. That region is on the opposite side of the country from where the first Ebola cases emerged.

And in Spain, doctors said tests showed that a Spanish nursing assistant infected with Ebola in Madrid was now completely clear of the virus. Teresa Romero, 44, had battled for her life after she tested positive Oct. 6.

One of the two vaccines that Kieny mentioned was developed by the U.S. National Institutes of Health and GlaxoSmithKline from a modified chimpanzee cold virus and an Ebola protein. It is in clinical trials now in the U.K. and in Mali and will be used in trials in Lausanne, Switzerland, by the start of February.

The second front-runner, developed by the Public Health Agency of Canada and known as VSV-EBOV, has been sent to the U.S. Walter Reed Army Institute of Research in Maryland for testing on healthy volunteers, with preliminary results about its safety expected by December. The next stage would be to test it more broadly, including among those directly handling Ebola cases in West Africa.

Canada has donated 800 vials of the experimental vaccine to WHO but the shipment was delayed by a Lufthansa pilots' strike. Those are now expected to arrive in Switzerland on Wednesday for testing coordinated by the U.N. health agency among volunteers at the University Hospital of Geneva, and volunteers in Hamburg, Germany, and in Gabon and Kenya, Kieny said.

"These data are absolutely crucial to allow decision-making on what dose level should go in the efficacy testing in Africa," Kieny said. "We expect, we hope, to have a go-ahead by the end of the month."

That would allow the vaccine to be shipped for use in Africa immediately afterward.

Kieny said decisions about "which strategy to use and how and where and who" regarding the vaccines will be made in the next few weeks. Then vaccines will be given to health workers and select segments of the general population "early in 2015, in January."

At a separate news conference, WHO spokeswoman Fadela Chaib promised a thorough public audit of the agency's early missteps — and those by countries and partner organizations — in responding to the Ebola crisis.

"There is certainly a wish and a will to have this review," she said. "We know many elements need to be explained in the future. ... WHO will do that, but in the future; now our focus is on the response."

The U.N.'s emergency committee on Ebola plans to meet later this week in Geneva to study the outbreak further and decide what more should be done.

The East African nation of Rwanda, meanwhile, was singling out travelers from the three West African nations for special treatment, as well as people from Spain and the U.S., where a very limited number of Ebola cases have emerged.

The Rwandan Ministry of Health said Tuesday that all passengers from those five nations will have their temperatures taken upon arrival. If a passenger has a fever, they will be denied entry. If there is no fever, the visitors still must report their health condition daily to authorities.

The U.S. Embassy in Rwanda urged Americans who may have a fever or who have traveled to Ebola countries "to weigh carefully whether travel to Rwanda at this time is prudent."

No Ebola cases have emerged in Rwanda.

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AP reporters Maria Cheng in London and Edmund Kagire in Kigali, Rwanda contributed to this report.