Ebola Vaccine

The Ebola epidemic may have largely subsided, but preventing another outbreak of the disease remains critical. Now, a new vaccine is giving public health experts reason to be optimistic.

In several global phase 1 trials, the rVSV-ZEBOV vaccine triggered strong anti-Ebola immune responses among participants while producing only mild side effects. The results of the trials were published in The New England Journal of Medicine.


“The prompt, dose-dependent production of high levels of antibodies following a single injection and the overall favorable safety profile of this vaccine make rVSV-ZEBOV a promising candidate that might be particularly useful in outbreak interventions,” said lead trial investigator Richard T. Davey, M.D., of the National Institute of Allergy and Infectious Diseases (NIAID), in a statement.

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How the Vaccine Came to Be

The rVSV-ZEBOV vaccine was first developed at the Public Health Agency of Canada. The agency then licensed the vaccine technology to NewLink Genetics Corp., which sold the rights to Merck & Co. Inc. for $50 million.

rVSV-ZEBOV is derived from the cattle virus rVSV, which scientists engineered to produce a Zaire strain of the Ebola virus (ZEBOV).

rVSV-ZEBOV is also one of two experimental vaccines tested in a recent phase 2 Liberian clinical trial. Researchers tested the safety and efficacy of both rVSV-ZEBOV and the chimpanzee-derived cold virus cAd3-EBOZ vaccine (developed by GlaxoSmithKline) in the Partnership for Research on Ebola Vaccines in Liberia (PREVAIL). Scientists said both of the vaccines appeared to be safe.

“We are grateful to the Liberian people who volunteered for this important clinical trial and encouraged by the study results seen with the two investigational Ebola vaccine candidates,” said NIAID director Anthony S. Fauci, M.D., in a statement. “Now we must move forward to adapt and expand the study so that ultimately we can determine whether these experimental vaccines can protect against Ebola virus disease and therefore be used in future Ebola outbreaks.”

Until a safe and effective vaccine is available, the world will continue to be underprepared for the next Ebola outbreak.
Anthony S. Fauci, National Institute of Allergy and Infectious Diseases

Researchers conducted phase 1 trials of rVSV-ZEBOV in the United States, Africa, and Europe. Participants in the studies experienced a high antibody response that improved as the dose of the vaccine increased. No serious adverse effects were reported among participants, but some people did experience symptoms such as fever and pain. 

The trial that took place in Geneva was put on hold last year after 11 of the 51 participants developed arthritis. It resumed in January.

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Ebola Outbreak Still Affecting Parts of Africa

To date, there have been more than 24,000 cases of Ebola and 10,000 deaths as a result of the latest viral outbreak. Although the Ebola epidemic has all but abated in the United States, the disease continues to impact some regions, particularly in West Africa.

“The outbreak is slowly coming under control, thanks to extraordinary and multifaceted efforts in the affected nations,” Fauci said. “However, there still are no licensed specific therapies or vaccines for Ebola. Until a safe and effective vaccine is available, the world will continue to be underprepared for the next Ebola outbreak.”

Several Ebola vaccines are currently in the works. Other treatments are also in development.

The World Health Organization hopes for a “safe and effective” vaccine by the end of this year. 

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