A single shot of a fast-acting, experimental Ebola vaccine successfully protects monkeys from the deadly virus after only one month. If this vaccine proves similarly effective in humans, it may one day allow scientists to quickly contain Ebola outbreaks with ring vaccination -- the same strategy successfully used in the past against smallpox, according to a study.

This finding is the result of collaboration between scientists at the Dale and Betty Bumpers Vaccine Research Center (VRC), part of the National Institute of Allergy and Infectious Diseases (NIAID), and scientists at the United States Army Medical Research Institute of Infectious Diseases (USAMRIID) at Fort Detrick, MD.

Under the directorship of Gary Nabel, scientists at the VRC have been pursuing the so-called "prime-boost" vaccine strategy against a variety of infectious diseases. Prime-boost is a two-part process: First, an injection of non-infectious genetic material from the disease-causing microbe primes the immune system to respond. Second, several weeks later, an injection of attenuated carrier viruses containing key genes from the microbe substantially boosts the immune response.

The VRC scientists found that the boost alone produces a quicker but weaker immune response as compared with the prime-boost strategy. Knowing that time is critical when fighting Ebola, the scientists decided to test whether the boost's fast response was strong enough on its own to protect against the disease. To perform this test, they collaborated with colleagues at USAMRIID, who had the necessary facilities and expertise and who had developed good animal models for the experiment.

The VRC scientists immunized eight monkeys with a single boost injection, consisting of attenuated carrier viruses containing genes for important Ebola antigens. The monkeys were then delivered to USAMRIID where they were injected with an Ebola virus strain obtained from a fatally infected person from the former Zaire in 1995. The single vaccine injection completely protected all eight animals against Ebola infection, even those who received high doses of the virus.