Monkey study: Ebola vaccine works, needs booster

New monkey studies show that one shot of an experimental Ebola vaccine can trigger fast protection, but the effect waned unless the animals got a booster shot made a different way.
     
Some healthy people are rolling up their sleeves at the National Institutes of Health for the first human safety study of this vaccine in hopes it eventually might be used in the current Ebola outbreak in West Africa.
     
The NIH on Sunday published some of the key animal research behind those injections. One reason the vaccine was deemed promising was that a single dose protected all four vaccinated monkeys when they were exposed to high levels of Ebola virus just five weeks later, researchers reported in the journal Nature Medicine.
    
 Is five weeks fast enough?
     
That's in line with other vaccines routinely used today, and fortunately it didn't take multiple doses to trigger that much protection, said Dr. Anthony Fauci, director of NIH's National Institute of Allergy and Infectious Diseases, whose employees led the work.
     
The bigger challenge is that the protection wanes over time.
    
Researchers exposed monkeys to Ebola 10 months after vaccination, and this time only half were protected.
     
Partial protection is better than none, Fauci said. But the goal is long-lasting protection, so it was time to try booster shots. The vaccine is made with a chimpanzee cold virus, used as a delivery system for pieces of an Ebola gene. The researchers tried simply giving another dose as a booster two months later. That didn't work well enough.
     
So they tried a different approach called "prime-boost." The first dose, to prime the immune system, was that original chimp virus-based Ebola vaccine. But...