Experimental vaccine used in Ebola exposure case

Dr. Stephan Guenther, head of the Bernhard Nocht Institute for Tropical Medicine in Hamburg, where the researcher was working, said tests so far show the scientist is healthy and free of the virus.

The peak period for an outbreak during the 21-day Ebola incubation period passed this week, he said.

"We are now on the downside," Guenther told The Associated Press, noting that with each passing day the chance of infection taking root diminishes.

It's not entirely clear the researcher was actually infected with the virus. At the time of the accident, she was wearing three layers of protective gloves, and though the needle stuck her, the plunger of the syringe was not pushed so it's not certain the virus entered her bloodstream.

That means scientists may never know if the vaccine worked or she was just lucky.

There are two other known accidents involving researchers who came into direct contact with a similar strain of Ebola. A Russian researcher died, and a British scientist became ill but survived.

After the needle stick, Guenther knew he had to act swiftly.

He rushed an e-mail to fellow scientists in the Ebola research community. One was Dr. Heinz Feldman, chief of the virology laboratory at the Rocky Mountain Laboratories, a U.S. National Institutes of Health research facility in Hamilton, Mont.

"We considered this as serious as (the Russian) case, in terms of the exposure," Feldman told the AP in a telephone interview last weekend.

Feldman was part of an international group of experts from the U.S. Centers for Disease Control and Prevention, the U.S. Army Medical Research Institute of Infectious Diseases, the Canadian Public Health Agency, Boston University and the University of Texas Medical Branch. Feldman, Guenther and several other experts took part in the teleconference debating the options. These included a live vaccine never before tried on humans, another treatment designed to interfere with the virus' ability to multiply, or an anticoagulant that Army research found had saved the lives of monkeys exposed to Ebola.

The option that emerged as the strongest was the vaccine, which had been developed by Feldman and collaborating researchers at several institutions. Much of the key work was done about nine years ago at a microbiology research lab run by the Canadian government in Winnipeg, Manitoba, where Feldman worked at the time.

Although the vaccine is based on a different kind of virus, researchers used genetic engineering to make the virus look like Ebola, triggering an “immune system response”.

In a 2008 study, Feldman and other researchers showed that when given 20 minutes after a lethal dose of Ebola virus, four of eight monkeys survived. There were no side effects, Feldman said.

Using the experimental vaccine, "was to save her life, that was the priority," Feldman said. It might have been five years or more before it was tried on humans because of additional animal studies and production issues, he added.

Guenther expressed hope the case would attract funding for more research in the field of such vaccines.