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With this latest outbreak, the development of one experimental Ebola vaccine is being fast-tracked, according to National Institute of Allergy and Infectious Diseases director Anthony Fauci, and human clinical trials are slated to kick off in September. Nonetheless, it could be years before its safety and effectiveness in humans is firmly established.
Another challenge of coming up with a vaccine to treat a deadly virus like Ebola is that researchers can’t easily — or ethically — test it on humans, according to Nancy Sullivan, chief of the Biodefense Research Section of NIAID’s Vaccine Research Center, and who in 2010 led the team that created an experimental vaccine that protected monkeys against two lethal strains of Ebola.
“We obviously can’t expose people to the Ebola virus” in order to know whether a vaccine is effective, Sullivan said. The alternative is to vaccinate high-risk human populations as a means of testing such a drug. But that’s also problematic because Ebola outbreaks are so sporadic and hard to predict — “unless we vaccinate all of Africa, which isn’t feasible,” she said.
Instead, scientists use what's known as the FDA's "animal rule," in which the efficacy of a vaccine is tested on animals, and that data is used to prove it could be safely used in humans. So far, just a few treatments have been approved using that rule, such as treatments for botulism and anthrax exposure.
In terms of the experimental Ebola treatment taken by two U.S. aid workers who contracted the virus caring for Ebola patients in Liberia, normally the U.S. Food and Drug Administration (FDA) would have to sign off on administering a drug it hasn’t approved for human use.
But this treatment, which is called ZMapp — a cocktail of two drugs that showed promise treating monkeys infected with Ebola — was given to Dr. Kent Brantly and missionary aid worker Nancy Writebol while they were still in Liberia. Samaritan’s Purse, the international aid organization Brantly was working with, contacted the Centers for Disease Control and Prevention (CDC) seeking experimental drugs, after which an NIH scientist in Liberia directed the group to the biotechnology companies currently developing treatments, according to NIAID. Both Brantly and Writebol gave their informed consent that they understood the risks of taking a treatment that had never been used in humans, CNN reported Monday.
ZMapp is a cocktail of what are called monoclonal antibodies, which bind to the virus to inactivate it. The antibodies were developed in the cells of tobacco plants by Kentucky Bioprocessing, which is owned by tobacco giant Reynolds American.
Mapp Biopharmaceutical said in a statement that "very little of the drug is currently available" because its safety has yet to be tested in humans, but the company's commercialization arm is reportedly working to produce more of the experimental serum.
On Wednesday, three of the world's top Ebola specialists — including Peter Piot, one of the scientists who discovered the virus back in 1976 — called for experimental drugs and vaccines to be offered to people in West Africa, too.
"African governments should be allowed to make informed decisions about whether or not to use these products — for example to protect and treat healthcare workers who run especially high risks of infection," wrote Piot, director of the London School of Hygiene and Tropical Medicine; Jeremy Farrar, a tropical medicine and global health professor at Oxford University; and David Heymann, head of the Center on Global Health Security at the U.K.-based Chatham House, in a joint statement.
And in a sign of the urgency to contain Ebola in West Africa, the World Health Organization said Wednesday afternoon that it would convene a panel of medical ethicists next week to explore the use of the experimental treatment in Guinea, Sierra Leone, Liberia and Nigeria.