Ebola vaccine: first large-scale trial begins in West Africa

The first large-scale trial of an experimental Ebola vaccine is to begin today in one of the West African countries worst affected by the disease, following a successful preliminary safety trial.

The batch of vaccines, developed by the British pharmaceutical giant GlaxoSmithKline, was transported under tight security to an unknown location in Liberia, the BBC reports. Up to 30,000 volunteers in the country are expected to be involved in the trial, with a third receiving the vaccine.

The vaccine contains a small amount of the virus which scientists hope will trigger an immune response that will protect against infection.

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Stephen Kennedy, the senior Liberian scientist involved in the trials said that the vaccine posed no risk to volunteers. "It is a weak strain and it cannot and will not cause Ebola, so it is impossible that any one of the volunteers will contact Ebola from the vaccine," he said.

GlaxoSmithKline's global vaccines chief Dr Moncef Slaoui described the shipment as "a major achievement", which "shows that we remain on track" with accelerated development of the Ebola vaccine.

"The initial phase one data... are encouraging and give us confidence to progress to the next phases of clinical testing, which will involve the vaccination of thousands of volunteers, including frontline healthcare workers," he said.

The company stressed, however, that the vaccine was still in its development phase and its long-term safety and efficacy would have to be established before it could be used on a wider scale.

"Any potential future use in mass vaccination campaigns will depend on whether the World Health Organization (WHO) regulators and other stakeholders are satisfied... and how quickly large quantities... can be made," said Slaoui.

Last month, the WHO said that the outbreak in West Africa had reached a turning point, as the number of new infections continued to decline, but warned against complacency in the fight to eradicate the disease entirely.

Paradoxically, this encouraging news may have a negative impact on the vaccine trial. "Because case numbers are starting to come down, it will become harder and harder to show if the vaccine is having any impact," Professor Jonathan Ball, a virus expert based at Nottingham University, told the BBC.

There is currently no proven vaccine or cure for Ebola and the unprecedented scale of the outbreak prompted governments, pharmaceutical companies and international health organisations to fast track the development of safe and effective treatments.

There are several other promising vaccines and treatments currently in development, with reports that the experimental drug zMapp, which was given to several Western healthcare workers who later recovered, will be trialled in the coming weeks.

The deadliest Ebola outbreak in history has so far claimed at least 8,641 lives and almost 22,000 people have been confirmed infected, although that number is expected to be much higher in reality.