MONROVIA, Liberia -- A large-scale human trial of two potential Ebola vaccines got under way in Liberia's capital Monday, part of a global effort to prevent a repeat of the epidemic that has now claimed nearly 9,000 lives in West Africa.
The trials in Liberia are taking place after smaller studies determined that the vaccines were safe for human use. By comparing them now with a placebo shot, scientists hope to learn whether they can prevent people from contracting the ghastly virus that has killed some 60 percent of those hospitalized with the disease.
Yet despite the trials' promise, authorities still must combat fear and suspicion that people could become infected by taking part. Each vaccine uses a different virus to carry non-infectious Ebola genetic material into the body and spark an immune response.
On Sunday in one densely populated neighborhood of Monrovia, musicians sang songs explaining the purpose and intent of the trial in a bid to dispel fears.
B. Emmanuel Lansana, 43, a physician's assistant, was the first to receive doses on Monday. Two shots were administered at different points on his right arm. His wife had expressed apprehension about the vaccine trial, but Lansana said he still wanted to take part.
"From the counselling, all of the reservations I have were explained, my doubts were cleared," he said in a room where he was being observed for 30 minutes afterward.
Up to 600 volunteers are taking part in the first phase, and trial organizers have said eventually as many as 27,000 people could take part.
"We are targeting about 12 persons for today and hopefully the number will increase as we go alone," Wissedi Sio Njoh, director of operation with the vaccination campaign, told The Associated Press.
The World Health Organization says the Ebola epidemic has infected more than 22,000 people and claimed more than 8,800 lives over the past year. Without a vaccine, officials have fought the outbreak with old-fashioned public health measures, including isolating the sick, tracking and quarantining those who had contact with them, and setting up teams to safely bury bodies.
Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, has said that both experimental vaccines showed promise in first-stage human safety tests. One was developed by the National Institutes of Health and is being manufactured by GlaxoSmithKline. The other was developed by Canadian health officials and is licensed to two U.S. companies, NewLink Genetics and Merck.
The vaccine trials come as the three most affected countries -- Guinea, Sierra Leone and Liberia -- appear to be making strides against the Ebola epidemic first identified last March. The U.N. health agency said last week that the countries had reported fewer than 100 cases in the past week, for the first time since June.
At the same time, scientists are raising concerns that the virus may be mutating, potentially complicating the search for an effective vaccine or treatment.
"We know the virus is changing quite a lot," human geneticist Dr Anavaj Sakuntabhai told the BBC.
It is not unusual for a virus to mutate as it is spread from person to person. The BBC noted a previous study by the World Health Organization which showed the Ebola virus mutated considerably within the first few weeks of the outbreak in Sierra Leone. "This certainly does raise a lot of scientific questions about transmissibility, response to vaccines and drugs," WHO reported. "However, many gene mutations may not have any impact on how the virus responds to drugs or behaves in human populations."
While mutation could potentially make the virus even more contagious or lethal, global health officials say it is extremely unlikely to fundamentally change the way the disease is transmitted. Ebola is spread through contact with infected bodily fluids; experts say it cannot become airborne.
"Scientists are unaware of any virus that has dramatically changed its mode of transmission," WHO writes. "That virus has probably circulated through many billions of birds for at least two decades. Its mode of transmission remains basically unchanged. Speculation that Ebola virus disease might mutate into a form that could easily spread among humans through the air is just that: speculation, unsubstantiated by any evidence."
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