Media playback is unsupported on your device Media caption Sir Andrew Witty, GSK: "This certainly gives us very significant cause for optimism"

The devastation of the Ebola outbreak in parts of West Africa has been one of the most shocking and distressing stories of the year.

Tonight there is a glimmer of hope - the first evidence that a vaccine could be available for health workers and others battling to bring the virus under control.

Ultimately, it could mean a vaccine for everyone in areas at risk.

Sir Andrew Witty, the chief executive of GSK, told the BBC that new clinical data published tonight was "very encouraging" and that a viable vaccine could be available in the second half of next year - If these early trials continue to provide positive results.

'Very encouraging'

The National Institutes of Health (NIH) in America has just released the first trial data for the vaccine that GSK is working on in its laboratories in Italy and Belgium.

Twenty adults were tested and an immune response to Ebola was prompted in each of them. The vaccine was also "well tolerated" by each of the people tested.

"It's a very encouraging first signal," Sir Andrew told me.

"Whether it's a breakthrough depends on making sure that all the rest of data over the next few weeks and months is in line. But this certainly gives us very significant cause for optimism.

"We've been looking at a potential Ebola vaccine, we've been looking at its basic safety and whether or not it can generate an immune response in healthy volunteers - and the data is very encouraging.

"But we need to put it into context - this is a very accelerated development programme and this is the first bit of data.

"It's the first piece of what will be a jigsaw of information that we are going to gather over the next five or six weeks before we move to the next stage."

Further trials

We are busy working out how we scale up manufacturing capacity, so that as we move into the second half of next year we would be in a position to manufacture very large quantities Sir Andrew Witty, GSK boss

Of course, as Sir Andrew says, any developments must be kept in perspective and there are a number of other trials still to report this year.

Any of those could throw up major problems in the vaccine's progress.

Image copyright AFP Image caption Artwork of Ebola virus particle

The NIH is certainly encouraged by these initial findings.

"The unprecedented scale of the current Ebola outbreak in West Africa has intensified efforts to develop safe and effective vaccines, which may play a role in bringing this epidemic to an end and undoubtedly will be critically important in preventing future large outbreaks," said Anthony Fauci, of the NIH's National Institute of Allergy and Infectious Diseases.

"Based on these positive results from the first human trial of this candidate vaccine, we are continuing our accelerated plan for larger trials to determine if the vaccine is efficacious in preventing Ebola infection."

Licence?

Sir Andrew said if the next series of smaller trials are similarly successful, then a major clinical trial of thousands of health workers in Sierra Leone and Liberia will take place early next year.

"If all goes well, the large scale clinical trial will be largely with healthcare workers, burial workers and people who are in close proximity to people with Ebola," Sir Andrew said.

"If the vaccine works, it will of course be a significant advantage to those workers.

"If overall that trial is successful, all things being equal, [that] should move us to a rapid licence for that vaccine.

"We are busy working out how we scale up manufacturing capacity, so that as we move into the second half of next year we would be in a position to manufacture very large quantities - that means millions of doses of the vaccine [being] available if governments and health authorities felt it necessary to go further than vaccinating health care workers."

Risk

That means a vaccine could be made available to resident populations in the affected countries.

As well as GSK, Johnson & Johnson and Merck are also proceeding with trials.

In this emergency situation, the pharmaceutical sector as a whole has been asked by G20 governments and the World Health Organisation to take on a considerable degree of financial and legal risk through this accelerated programme.

For example, the programme is not going through all the usual stages of a vaccine's development - which would normally take many years.

If something does go wrong in the future, the pharmaceutical sector does not want to be the only part of the process exposed to, for example, legal action.

To tackle that, Sir Andrew said that GSK is in discussions with governments of the G20, including America and the UK, about an indemnification agreement.

"We are not waiting for that to be settled [but] it is obvious there are some risks that companies should not be expected to carry on their own," Sir Andrew said.

"This is a very special circumstance.

"There is a risk [in the] development - and it is important to know that organisations like the NIH in America and the European Union are helping to support some of these trial costs - so that is an important contribution and shows good solidarity.

"In terms of the indemnity risk, those conversations go on - we have a good precedent for this with the pandemic influenza case of three of four years ago."

'Right thing'

Whether we are a big company or not, we are still humans. We are talking about people's lives here, every day counts, we get that Sir Andrew Witty, GSK boss

On that occasion governments agreed to offer GSK indemnities in return for supplies of its flu vaccine.

Sir Andrew said that the indemnity issue was not holding back development of the Ebola vaccine.

"We take our responsibilities very seriously to make sure that there is good access to our vaccines, even in countries which can't pay very much for it," he said.

"It sounds trite but in a situation like this you have to do the right thing. It turns out that on this project we are the leader in terms of time - the right thing to do was for us to commit all our energies to make this thing happen.

"We are doing that - we are taking risks, we are taking financial risks. We have taken decisions without being asked.

"We've taken decisions without the guarantee of compensation. I think that's the right human response to this crisis.

"Whether we are a big company or not, we are still humans.

"We are talking about people's lives here, every day counts, we get that, our employees get that. Our scientists are working 24/7 to deliver for those people in those camps."

Today's break-through is another important step on the journey to finding a vaccine against Ebola.