Monkeys are known to develop hemorrhagic fever symptoms that are similar to those observed in humans infected by these viruses. Demonstrating that these vaccines are safe and effective in monkeys is a promising indicator of their real potential for use in humans, the researchers said.

"When you see the tragedies these viruses cause, it's very frustrating that we can't do more to help people," said Heinz Feldmann, the lead investigator in this study who has been providing on-site rapid diagnostic support to the current Marburg outbreak in Angola.

"It'll be some time before we can use these vaccines in the field, but it's satisfying to know that we're getting closer."

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This is the first vaccine system, or platform, that has protected non-human primates from both Ebola and Marburg, according to the researchers

"In addition, the vaccine targets dendritic cells, which are the same cells that Ebola and Marburg attack," said Thomas Geisbert, co-author from the USAMRIID. "These cells are also important in generating a protective immune response. So the vaccine goes exactly where we want it to go."

The researchers developed the vaccines by replacing a surface protein in an animal pathogen, called vesicular stomatitis virus, with a surface protein from either the Ebola or Marburg viruses. Following extensive work including trials with mice and guinea pigs, the researchers proved their efficacy in primates.

"A single intramuscular injection of the EBOV (Ebola Virus) or MARV (Marburg Virus) vaccine elicited completely protective immune responses in nonhuman primates against lethal EBOV or MARV challenges. Notably, vaccine vector shedding was not detectable in the monkeys and none of the animals developed fever or other symptoms of illness associated with vaccination," they wrote in the paper

"The EBOV vaccine induced humoral and apparent cellular immune responses in all vaccinated monkeys, whereas the MARV vaccine induced a stronger humoral than cellular immune response. No evidence of EBOV or MARV replication was detected in any of the protected animals after challenge. Our data suggest that these vaccine candidates are safe and highly efficacious in a relevant animal model."

Canadian Health Minister Ujjal Dosanjh and Minister of State Carolyn Bennett highly praised the work of the scientists in developing the vaccine and providing support to the outbreak in Angola.

"This speaks volumes about the dedication and expertise of these individuals, and also what can be achieved through international collaboration," said Dosanjh in a statement.

Colonel Erik A. Henchal, commander of USAMRIID, said the study illustrates the benefits of collaborative research to develop medical countermeasures for biodefense.

"Relationships like this contribute to better science and ultimately better protection for military service members and civilians alike."