Ebola outbreak: 2 vaccines look safe, tests in West Africa delayed

The World Health Organization says the two leading Ebola vaccines appear safe and will soon be tested in healthy volunteers in West Africa.

After an expert meeting this week, WHO said there is now enough information to conclude that the two most advanced Ebola vaccines one made by GlaxoSmithKline and the other licensed by Merck and NewLink have "an acceptable safety profile."

In a press briefing on Friday, Dr. Marie-Paule Kieny, who heads WHO's Ebola vaccine efforts, said "the cupboard [for Ebola vaccines] is filling up rapidly."

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She said further trials in healthy people in West Africa, including health workers, are scheduled to start soon. Kieny added several other vaccines were being developed in the U.S., Russia and elsewhere.

Despite the temporary suspension of a trial of the Canadian-designed vaccine made by NewLink and Merck in December, Kieny said there was no sign of significant side-effects. That trial was put on hold while experts investigated reports of "transient, mild" joint pain in a number of participants. It was an unexpected side-effect but Kieny said it was not worrying enough to stop the vaccine's development. No such side-effects have been reported with the other vaccine.

Phase 1 trials are designed to see if a product is safe to use and to determine what the dose for a drug or vaccine should be. They are followed by larger Phase 2 and 3 trials that are designed to show if an experimental product actually works.

It will take the manufacturers another two to four weeks to be able to determine an appropriate dose, Kieny said.

That is a delay on previous plans. It had been hoped the first and the largest of the trials would start in Liberia by mid-January.

The next phase of trials will likely take about six months and manufacturers will ramp up their production at the same time, meaning millions of doses could be available later this year. It's unclear if that will be quick enough to help slow the epidemic, which is mostly on the decline. So far, Ebola is believed to have sickened more than 20,000 people and killed about 8,000, the vast majority in Guinea, Liberia and Sierra Leone.

"We will have to take stock when we have the vaccines," said Helen Rees of the University of Witwatersrand, who chaired the WHO meeting. She said experts would have to consider at that point whether it's useful to vaccinate entire populations or focus only on high-risk groups.

Dr. Peter Piot, the co-discoverer of the Ebola virus, said he was concerned there might be too few cases to prove the vaccines worked, if they are effective. Still, he said every option should be pursued to stop the world's biggest-ever outbreak of Ebola.

"With Ebola, you need to find every last case and stop all transmission," he said. "It may be that we won't be able to do that without a vaccine," Piot said.