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.

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

Dr. 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. He and other researchers said that governments and the military developed a strong interest in making vaccines against Ebola and Marburg during the 1990's after a Soviet defector said that Russians had stockpiled the Marburg virus, weaponized it and packed it 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 Dr. Peter B. Jahrling, an author of the article and an expert on viruses and bioterrorism who used to work for the Department of Defense and is now a chief scientist at the National Institute of Allergy and Infectious Diseases, of the National Institutes of Health. "But I think a lot of people here also see the humanitarian aspects of providing vaccine to people who need it."

Dr. 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."

Newsletter Sign Up Continue reading the main story Please verify you're not a robot by clicking the box. Invalid email address. Please re-enter. You must select a newsletter to subscribe to. Sign Up You will receive emails containing news content , updates and promotions from The New York Times. You may opt-out at any time. You agree to receive occasional updates and special offers for The New York Times's products and services. Thank you for subscribing. An error has occurred. Please try again later. View all New York Times newsletters.

To make the vaccine, the scientists used another virus, V.S.V., 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 V.S.V. 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 V.S.V. to produce Marburg or Ebola proteins on its surface. The proteins cannot cause illness, but they provoked an immune response that protected the animals.

The monkeys were housed at a high-level biohazard laboratory at Fort Detrick, where the researchers, wearing space suits, watched them intently for signs of illness after they were injected with Marburg or Ebola.

Advertisement Continue reading the main story

"By Day 6, I have a very good idea of whether it's going to work or not," Dr. Geisbert said. "On Day 6 I was feeling really good. By the time we get to Day 10, if the animals haven't become sick or had any problems, we pretty much know it's worked. It is an incredibly good feeling. All the people on the team are high-fiving. I was communicating with Heinz and Steven every day, two and three times a day. 'How are the monkeys? How are the monkeys?"'

As the team pursues its research, other scientists are moving ahead with the previously developed Ebola vaccine, based on an inactivated version of another type of virus, an adenovirus, which can cause common cold symptoms in people. That vaccine, tested in 2003, also protected monkeys, and studies in people may begin this year.

Dr. Jahrling, who has worked on both types of vaccine, said the government was paying for both approaches to cover its bets. He said he thought a vaccine based on an adenovirus would be ready before one based on V.S.V.

"They've got a runner on third with that one," he said, "and the other guys have a runner on first."

Dr. Jahrling added: "A little competition is good. It accelerates everybody. If nobody's behind them they kind of slow up."

But Dr. Gary Nabel, head of the Vaccine Research Center at the N.I.H. infectious disease institute, who has been working on the adenovirus vaccine, said: "I don't look at it as a race. For me, the adversary is the virus and whatever gives us the best opportunity to defeat the virus is what we need to go with."