"These trials are about to begin for the two lead vaccines," WHO assistant director general Marie-Paule Kieney said during the second high-level meeting on Ebola vaccines, access and financing here.
Third phase clinical trials for the two vaccines-- developed by GlaxoSmithKline (GSK) and Merck-- will begin in West Africa at the end of this month or early next month.
The tests would be conducted in Liberia, Sierra Leone and Guinea, the epicentre of the Ebola crisis. The design sets, however, will be different in all the three countries.
While Liberia will use randomised control trials in three arms with 9000 individuals in each arm and will test two vaccines by the end of January, Sierra Leone will test one vaccine on 6000 volunteers in February.
Guinea will use the ring vaccination method which was used for the eradication of small pox on 90 rings of people. The mean population of a ring is 50 people.
Community mobilisation for the trials have already begun in Liberia. Health workers on the frontlines against the epidemic are considered priority for the tests in Sierra Leone.
Merck vaccine- VSV-ZEBOV- hit a roadblock recently when phase-I testing were called-off after the volunteers developed arthritis/joint pain.
Kieney called the side effects "transient and sufficiently mild and not sufficient concern to call off the development of the vaccine".
The GSK vaccine- cAd3-EBO- published the results of the phase I trial in the New England Journal of Medicine in November last year.
Johnson and Johnson too has been in discussion for the development of two different types of vaccine, one that will protect very quickly in case of an outbreak and another that belongs to the preventive vaccine regimen.
Though research and development for Ebola vaccines is mostly being done in the US, Russia and China are also working on it.
One of the shortfalls of the vaccines is the need for storage at -80 Fahrenheit. Kieney said manufacturers are working to change the condition of storage and stabilise the formulation so it could be stored at higher temperatures.
Kieney emphasised that if 2014 will be remembered for Ebola virus challenging humanity, 2015 will be remembered for using the best scientific minds to fight back.
"In this outbreak we would have limited choice of what would work," Kieney said adding there are possibilities to check better Ebola vaccines after the epidemic.
Helen Rees, chair of the meet on Ebola vaccines, said first generation vaccines are always a challenge.
Ebola virus has claimed more than 8,000 people in West Africa and has affected 21,000 people worldwide.

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