Research assistant works on a vaccine for Ebola at The Jenner Institute in Oxford, southern England January 16, 2015. [Photo/Agencies]

LONDON - First results from a human trial of an Ebola vaccine from GlaxoSmithKline show it is safe and generates an immune response, scientists said on Wednesday, but larger trials are needed to see if it protects and if a booster is needed.

The vaccine is being developed by the US National Institutes of Health (NIH) and GSK against the Zaire strain of Ebola -- the one circulating in West Africa -- and the first doses for a larger trial arrived in Liberia last week.

That trial is the first of several mid-stage studies planned for West Africa and aims to test GSK's vaccine and one from Merck and NewLink. Johnson & Johnson and Bavarian Nordic have a vaccine in early-stage clinical tests.

The early-stage Phase I trial of GSK's vaccine was primarily designed to test safety, but Adrian Hill, who led the work at Oxford's Jenner Institute, said it was "encouraging" that the shot also prompted responses from the immune system.

"The safety profile is pretty much as we'd hoped and the immune responses are okay, but not great," he said.