The first people vaccinated with an experimental Ebola shot being developed by Merck and NewLink have had no serious side effects so far, but a few experienced mild fever, Swiss researchers said on Tuesday.

The shot, one of several being fast-tracked through clinical trials in the hope they can be approved for use in the Ebola epidemic raging in West Africa, is undergoing initial human safety tests at the University Hospitals of Geneva.

"After his or her injection, each volunteer was kept under observation for 1.5 hours at the clinical trials unit," scientists at the Swiss hospital said in a statement.

"To date, no major side effects have been observed after the injections, which triggered the expected inflammatory responses. They (the inflammatory responses) have been weak to moderate, with limited cases of mild fever," it added.

Since 10 November, 34 volunteers have been vaccinated with the shot, known as VSV-ZEBOV Ebola vaccine, at the request of the World Health Organization (WHO).

Trials have also begun in the United States, Canada, Germany and Gabon, and similar trials should start soon in Kenya.

This is the first data from human testing of the Merck/Newlink shot. It follows positive news last week about a GlaxoSmithKline candidate Ebola vaccine, which caused no serious side effects and produced an immune response in 20 volunteers in early-stage trials.

A version of GSK's vaccine targeting only the Zaire strain of Ebola which is causing the current outbreak is undergoing safety trials in Britain, Mali and Switzerland.

A trial of an Ebola vaccine from Johnson & Johnson is scheduled to start in January.

The Ebola epidemic is the largest ever recorded and has so far infected around 16,000 people, killing almost 6,000 of them, according to latest WHO figures. The vast majority of cases and deaths have been in Guinea, Sierra Leone and Liberia.

Some Ebola experts say it is unlikely the epidemic can be brought under control without the use of a vaccine, which if successful could protect healthy people from being infected with the contagious and deadly virus.

Merck announced last month that it would buy the rights to NewLink's vaccine for $50 million.