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U.S. scientists begin testing experimental Ebola vaccine


The first test in humans of an experimental vaccine against the deadly Ebola virus began yesterday, U.S. government scientists said.

The vaccine, administered by injection, was designed to try to prevent outbreaks of the lethal hemorrhagic fever where it occurs naturally in Africa. It is also a bid to thwart any efforts to use the highly infectious virus as a bioterrorist agent.

As part of a standard three-stage process, the first phase involves testing the vaccine's safety. Scientists also plan to measure immune responses among volunteers receiving the shots.

No effective treatment exists against the viral infection, which kills up to 90 percent of victims quickly from severe internal bleeding. Ebola was discovered in 1976 in the Republic of Congo, then called Zaire. This week, the World Health Organization reported a new outbreak of Ebola in that country, attributing 11 deaths in as many cases to it.

The experimental DNA vaccine is synthesized using modified, inactivated genes from the Ebola virus. Because it does not contain any infectious material from the virus, recipients cannot get the disease, said Dr. Gary Nabel, who directs the Vaccine Research Center at the National Institute of Allergy and Infectious Diseases in Bethesda.

Researchers plan to test the vaccine on 27 people. Volunteers are expected to receive three injections of either the experimental vaccine or a placebo at the institute over two months. Then they will be monitored for one year.

Nabel said in a telephone interview that only a handful of individuals, mostly institute employees, had volunteered for the study and that his team needed at least 20 more volunteers. Details are posted at www.clinicaltrials.gov.

The vaccine is made by Vical, a biotechnology company in San Diego that has collaborated with Nabel's team as it tested the vaccine on animals.

The goal is to use the Vical vaccine and another one to protect against Ebola in a prime-boost strategy. Under those conditions, the Vical vaccine would be given first to prime the immune system. Then a different vaccine, which uses an adenovirus (that causes colds) to bolster the immune system primed by the Vical vaccine. The second vaccine is still being developed for human use; the first tests in volunteers are expected to begin next year, Nabel said.

Tests of the prime-boost strategy are expected to begin in 2005. But the schedule depends in part on the findings from the current tests.

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