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Quest for an Ebola vaccine proves difficult


A year ago, the World Health Organization (WHO) declared an Ebola outbreak in West Africa. Since then, the WHO estimates that almost 25,000 individuals in the region have been sickened and over 10,000 have been killed by this deadly virus. While political leaders have pressed for a vaccine to protect vulnerable civilians, there currently is no Ebola vaccine that is licensed for use in humans.The virus currently has a 40 percent survival rate.  Those who contract it lose about 8 to 10 liters of water every day, and death occurs in 7 to 21 days.

The World Health Organization says at least 12 million doses of the vaccine would be needed to protect the adults in Liberia, Guinea and Sierra Leone and scientists are under pressure to create a vaccine quickly.

One frontrunner vaccine being developed by the NIH and National Institute of Allergy and Infectious Diseases (NIAID) is based on a chimpanzee adenovirus. Adenoviruses are known for causing upper respiratory infections and flu-like symptoms. In this particular vaccine platform, the adenovirus would carry signatures from the Ebola virus that hopefully the body will recognize when a real Ebola virus does enter the system.

However, Patricia Repik, a National Institutes of Health virologist, says the nature of the virus presents many challenges in vaccine development. For example, clinical trials would begin with testing the vaccine on small mammals, but your typical lab mice don’t get sick from Ebola.

“The vaccine developers have had to mutate the Ebola virus to make it infect these small mammals, but that doesn’t replicate the natural disease, so it’s been  very difficult,” said Repik.

A study last August in the journal Science also showed that the virus is mutating rapidly as it spreads through West Africa. In other words, creating an Ebola vaccine is like chasing after a moving target.

Repik says that Ebola vaccine candidates are being tested in the U.S. to measure their safety before being approved for use in the affected West Africa countries.

“They’re evaluated in the US because we didn’t know their safety,” said Repik.  “If you just went into a population already sickened by the ebola, you wouldn’t know if people were dying from Ebola or having problems with the vaccine. There would be no way to test that.”

Repik spoke at the 10th Annual “New Technologies, New Vaccines” conference in Wilmington, which was hosted by Newark-based Fraunhofer Center for Molecular Biology.