Governments and the military developed a strong interest in making vaccines against Ebola and Marburg during the 1990s after a Soviet defector said that the Russians had stockpiled the Marburg virus. The defector said the virus had been weaponized and packed into warheads for possible use in attacks on cities or battlefields.

Two new vaccines, one for Marburg and one for Ebola, were 100 percent effective in a study of 12 macaques being published Monday in the journal Nature Medicine. Monkeys given just one shot of the vaccine and later injected with a high dose of the virus did not even get sick. Normally, all the animals would be expected to die.

The Marburg and Ebola viruses are closely related, and in both people and monkeys they cause hemorrhagic fevers that can be fatal within a week. There is no vaccine or treatment for either disease. Death rates in people can be high, sometimes exceeding 80 percent or 90 percent.

Angola Struggling to Contain Marburg

Angola, where a Marburg epidemic was first detected in March, is still struggling to contain the disease, which has killed 340 of 408 victims. The virus is spread by contact with blood, saliva, vomit or other fluids from sick patients.

The two new vaccines are still experimental, and will not be ready even to be tested in people for at least two years. If human trials are successful, products might be ready for licensing five or six years from now, the researchers said.

The vaccines would not be used for routine immunization, but would be given to health workers in high-risk areas, virus researchers and people who had been exposed to the disease, like relatives and other close contacts of sick patients. Eventually, it might be possible to combine the vaccines to protect people from both diseases with a single shot.

The new vaccines are not the first to protect monkeys. An earlier one, first proved in 2003, may go into safety studies in people in the United States later this year. Each vaccine has its advocates, and researchers say it is advantageous to have several candidates on the horizon.

Germ Warfare

The work described in Nature Medicine was done by scientists from the United States and Canada, led by Steven Jones and Heinz Feldmann of the Public Health Agency of Canada in Winnipeg, and Thomas Geisbert of the U.S. Army Medical Research Institute of Infectious Diseases at Fort Detrick, Maryland.

Jones said the goal of the research was to provide a vaccine that could be used to stop outbreaks like the one in Angola, or to protect people from germ warfare. Jones and other researchers said that governments and the military developed a strong interest in making vaccines against Ebola and Marburg during the 1990s after a Soviet defector said that the Russians had stockpiled the Marburg virus. The defector said the virus had been weaponized and packed into warheads for possible use in attacks on cities or battlefields.

"Marburg and Ebola are not as significant threats as smallpox would be, but one could wreak incredible human health tragedies in this country and could probably create a huge economic burden even if the diseases didn't spread like wildfire," said Peter Jahrling, an author of the article and an expert on viruses and bioterrorism who used to work for the U.S. Department of Defense and is now a chief scientist at the National Institute of Allergy and Infectious Diseases. "But I think a lot of people here also see the humanitarian aspects of providing vaccine to people who need it."

Genetic Alteration

Cathy Roth, head of the emerging and dangerous pathogen team at the World Health Organization, said: "This work is very interesting, very exciting and very promising. There's a long way to go before this vaccine could be put into people. But we really do hope it is pursued."

To make the vaccine, the scientists used another virus, VSV, for vesicular stomatitis virus, which causes a mouth disease in cattle but rarely infects people. They chose it because it has a similar genetic structure to the Marburg and Ebola viruses, and because other researchers have had success with it in developing vaccines.

They altered VSV by removing one of its genes -- the change makes it harmless -- and replacing it with a gene from either the Marburg or Ebola virus. The transplanted gene forced VSV to produce Marburg or Ebola proteins on its surface. The proteins cannot cause illness, but they provoked an immune response that protected the animals from Marburg or Ebola.