Human trials underway aiming to prevent another outbreak of the virus which has swept through west Africa

Hopes for an effective Ebola vaccine have been raised after trials of an experimental jab found that it gave monkeys long-term protection from the killer disease.

Animals that received a first shot of the vaccine and a booster two months later were immune to the infection for 10 months, according to US government researchers. If further trials show that the vaccine works safely in humans, it could be used to protect health workers and contain future outbreaks by immunising villagers living next to affected areas.

The findings will encourage scientists in the UK and elsewhere who have just begun human trials of an Ebola vaccine in the hope of preventing another outbreak of the virus which has swept through Guinea, Liberia, Sierra Leone and Nigeria, claiming more than 2,000 lives.

The World Health Organisation warned last week that the total death toll in African states could reach 20,000 before it could be brought under control. The infection is spread by contact with bodily fluids and causes fever, vomiting and severe bleeding.

Researchers led by Nancy Sullivan at the US National Institutes of Health (NIH) in Maryland tested two different vaccines on macaques. The first was based on a harmless monkey virus which had been modified to carry a protein from the Zaire strain of Ebola, responsible for the latest outbreak. A single shot of the vaccine protected the animals from the virus for several weeks. The same vaccine, developed by the US NIH and GlaxoSmithKline, has just gone into human clinical trials in the UK and will potentially be trialled in Mali and the Gambia.

The US researchers went on to test a second vaccine based on a modified cowpox virus. Monkeys that received the vaccine as a booster two months after the first vaccine were protected against lethal doses of Ebola for a full 10 months, according to a report in Nature Medicine.

The Guardian understands that UK researchers are keen to include the booster jab in future human trials.

Jonathan Ball, a molecular virologist at the University of Nottingham, said that a single jab that gave even a few weeks of protection could help to contain an Ebola outbreak.

"This is important as it would keep the dosing regimen simple and could still provide good protection in the sort of outbreak that we are seeing in western Africa at the moment," he said. "For longer-term protection to prevent future outbreaks one could envisage using the combination, the so-called prime / boost approach."

Martin Hibberd, professor of emerging infectious disease at the London School of Hygiene and Tropical Medicine, said the study "gives hope for a successful trial in humans".

On Friday, the UN chief, Ban Ki-moon, set the goal of stopping the worst-ever outbreak of the disease within six to nine months. The "next few weeks will be crucial," Ban said in New York, adding that this was an "international rescue call".

Meanwhile, authorities are ordering people in Sierra Leone to stay inside their homes for three days later this month as part of an effort to stop the spread of Ebola, a government spokesman said on Saturday. Abdulai Bayraytay said the government was telling people to stay inside their homes on 19, 20 and 21 September. The dates were chosen to give people enough time to stock up on food and other provisions before the ban on movement goes into effect, he said.

This piece was amended on 8 September to clarify that human clinical trials

of the Ebola vaccine could go ahead in Mali and The Gambia but have not yet done so.