A new experimental vaccine plus booster shot against Ebola protects monkeys for around ten months, federal researchers have found.

The U.S National Institutes of Health scientists said that vaccinated monkeys can develop immunity against the killer disease for around five weeks. A booster shot, scientists said, increases immunity for about 10 months. The researchers have now started testing the vaccine on human subjects, BBC reported.

"The good part of this vaccine is that at five weeks or earlier you get full protection," said Dr Anthony Fauci, the director of the US National Institute of Allergy and Infectious Diseases, told the BBC. "The sobering news is the durability isn't great, but if you give a boost, a second shot, you make it really durable."

"We knew this worked in the monkey months ago and based on this paper we started human trials," Fauci added.

Their research is published in the journal Nature Medicine.

The federal researchers as well as pharmaceutical giants such as GlaxoSmithKline, Johnson & Johnson and NewLink Genetics are all in the race to find a vaccine that can protect people against the deadly infection.

Ebola virus spreads via exposure to bodily fluids. The deadly disease has already claimed thousands of lives. The World Health Organization said that Ebola could kill 20,000 people in African countries before it is controlled.

In the current animal study, the researchers tested two different vaccines on macaques. The first vaccine had a harmless monkey virus (chimp adenovirus) that was genetically altered to carry an Ebola strain from Zaire. The Zaire strain is responsible for the latest outbreak. The second vaccine was a booster shot given at two months and was based on a modified cowpox virus, Guardian reported.

The animals received the second vaccine as a booster shot. The researchers found that the second vaccine protected monkeys for 10 months.

The vaccine used in the current study is similar to those being developed by GSK. According to Reuters, GSK already began trials on humans last Tuesday. J&J is starting clinical trials in the first few months of 2015.