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Ebola Vaccines: The Three Front-Runners

Companies race to find a cure

A vaccine against Ebola virus infection is urgently needed, and several companies are racing to test their experimental vaccines in an effort to halt the spread of the deadly disease. The Ebola virus has infected more than 20,000 people in West Africa and has killed at least 8,200, according to the World Health Organization (WHO).

Experts estimate that at least 100,000 doses of vaccine are needed to protect frontline health care workers. In addition, at least 12 million doses would be needed to vaccinate all adults in the three worst-affected countries of Guinea, Liberia, and Sierra Leone, according to WHO.

Currently, three experimental vaccines look promising. All are licensed to large pharmaceutical companies and are now being tested in humans. A new report on the website Live Science looks at each of these vaccines.

Johnson & Johnson is working on an investigational vaccine that contains modified versions of a human cold virus and the smallpox virus. It also contains bits of Ebola’s genetic material, which could provoke an immune response against the Ebola virus.

On January 6, the company said it had begun administering its vaccine to healthy volunteers in the United Kingdom in a phase I clinical study. Seventy-two people are receiving either the vaccine or placebo. The vaccine involves two shots: the first dose “primes” the immune system, while the second dose (given 1 or 2 months later) boosts the body’s immune response.

In earlier experiments conducted in collaboration with the National Institutes of Health (NIH), researchers found that the vaccine protected monkeys against the Zaire strain of the Ebola virus, which is causing the current outbreak, J&J said in September.

Janssen Pharmaceuticals, a subsidiary of J&J, is developing the vaccine together with Bavarian Nordic. More than 400,000 doses of the vaccine have been produced and could be used in larger trials by April.

Another Ebola vaccine, made by GlaxoSmithKline, is further along in development. The results of a phase I trial were published in November 2014 in the New England Journal of Medicine. The research showed that the vaccine, called cAd3-EBO, which the company developed in collaboration with the NIH, was well-tolerated and appeared to be effective.

The vaccine is made of a harmless cold virus that affects chimpanzees, but it is coated with proteins from the Zaire and Sudan strains of the Ebola virus.

In the study, 20 healthy adult volunteers in the U.S. received the vaccine and subsequently produced antibodies against the Ebola virus, Glaxo said. Now the company is preparing to test the vaccine in a larger cohort. The second phase of the study may start in February in Africa, according to a report from Reuters.

Finally, testing of an Ebola vaccine from Merck is back on its feet after hitting a bump in the road. Researchers began a phase I trial of the vaccine, called VSV-ZEBOV, in December 2014 but stopped the study when some of the volunteers reported joint pain. These symptoms, however, resolved without treatment, according to the University of Geneva Hospital in Switzerland, where the study was being conducted. The researchers resumed the trial using a lower dose of the vaccine, the hospital announced on January 5.

The VSV-ZEBOV vaccine consists of the vesicular stomatitis virus (VSV), which mainly infects animals. In the vaccine, one gene of VSV has been replaced with the gene that codes for the outer protein of the Zaire strain of the Ebola virus, according to the NIH. The vaccine was developed by researchers at the Public Health Agency of Canada’s National Microbiology Laboratory, and has been licensed to NewLink Genetics Corp. in Iowa, and to Merck & Company.

Source: Live Science; January 8, 2015.

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