Scientists are hopeful a vaccine against the deadly tropical disease Marburg virus could be developed.
Marburg is the from the same virus family as the deadly Ebola
Similar to the Ebola virus, Marburg causes internal bleeding leading to multiple organ failure in 90% of cases - there is no effective treatment.
A US-Canadian team writing in the Lancet say they have created a jab which appears to protect monkeys from Marburg's harmful effects.
Both the Marburg and Ebola viruses are considered potential bio-terror agents.
The Marburg virus was first detected in 1967. A large outbreak in Angola 2004-5 killed several hundred people.
Marburg, like Ebola, is a member of the filovirus family which cause severe haemorrhagic fever in humans and non-human primates.
Researchers from the US Army Medical Research Institute of Infectious Diseases (USAMRIID) and the National Microbiology Laboratory at the Public Health Agency of Canada carried out the work on this potential vaccine.
They created the vaccine known as recombinant VSV (rVSV), by taking a harmless virus and replacing one of its genes with a non-disease causing gene from the Marburg virus.
This enables the body to recognise Marburg and stimulates it to begin attacking it.
Five rhesus monkeys infected with the virus were then injected with the rVSV vaccines 20 to 30 minutes later.
A further three monkeys infected with Marburg were given a vaccine without the virus gene.
The team found that all of the monkeys treated with rVSV survived for at least 80 days, while those that did not succumbed to the disease within 12 days.
But the researchers admitted they were not sure why the vaccine worked.
Thomas Geisbert, who led the work, said the results were very encouraging.
"This is the first demonstration of complete post-exposure protection of non-human primates against a filovirus," he said.
The vaccine has already been shown to protect monkeys against the symptoms of the virus if inoculated prior to infection.
In an accompanying article in the Lancet, Stephan Becker, of the Robert Koch Institute in Berlin, said the development of the potential vaccine was good news.
But he warned that because of a "missing market" and the relatively low number of naturally occurring Marburg or Ebola virus infections, this vaccine would probably not be developed commercially.
"However, given the enormous amount of money funnelled into investigation of agents that are supposed to have bio warfare potential, further development of currently available experimental vaccines against highly pathogenic viruses should be possible."