Initial results of the human trial of the Ebola vaccine developed by GlaxoSmithKline (GSK) showed that it is safe for human use, with mild side effects.

GSK collaborated with the U.S. National Institutes of Health (NIH) in the development of the Ebola vaccine against Zaire, the strain circulating in West Africa. The developers were satisfied with the results of the early trial because it met their initial goal, which is to test for safety.

The British pharmaceutical company announced on Wednesday that has already delivered the first batch of vaccine in Liberia last week so they can test it on a larger sample.

The larger sample will include 30,000 volunteers including the frontline health workers. They will be divided into three groups: one to receive the GSK/NIH vaccine, one to receive the experimental vaccine of Merck-Newlink, and a placebo group, according to BBC News.

"The safety profile is pretty much as we'd hoped and the immune responses are OK, but not great," Adrian Hill, who led the work at Oxford's Jenner Institute, told Reuters.

The early-stage human trial included 60 healthy volunteers who received three different doses: low, medium and high. They were observed for 28 days for possible side effects and noted pain and reddening at the injection site, but nothing life-threatening. The researchers concluded that the vaccine is safe for human use, even if the immune response was weaker than the results they got from animal tests.

Hill admitted that there is no guarantee that the vaccine will effectively protect the people from Ebola.

"We still don't know whether it will provide protection against Ebola infection in a real-world situation," he said. "That's why trials in West Africa of this and the other vaccines in development, must begin as soon possible."

The result of the early-stage human trial was published in the Jan. 28 issue of the New England Journal of Medicine.