The Food and Drug Administration (FDA) has approved Ervebo (Ebola Zaire vaccine, live) for the prevention of disease caused by Zaire ebolavirus in individuals ≥18 years of age.

The approval was based on data from a study conducted in Guinea  in which 3537 contacts, and contacts of contacts, of individuals with laboratory-confirmed Ebola virus disease received either “immediate” (n=2108) or 21-day “delayed” vaccination (n=1429) with Ervebo. Results showed that the vaccine was found to be 100% effective; no cases of Ebola virus disease occurred ≥10 days after vaccination in the “immediate” cluster group, while 10 cases were noted in the 21-day “delayed” cluster group. 

Additional studies showed that antibody responses to Ervebo were similar among individuals who received the vaccine in Liberia (N=477), Sierra Leone (N=~500), and Canada, Spain and the US (N=~900). Safety was assessed in approximately 15,000 individuals, with the most commonly reported adverse reactions being pain, swelling, injection site reactions, headache, fever, joint and muscle aches and fatigue.

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The duration of protection conferred by Ervebo is unknown, as is its effectiveness when concurrently administered with antiviral agents, immune globulin, and/or blood or plasma transfusions. In addition, the vaccine is contraindicated in patients with a history of severe allergic reaction to any component of the vaccine, including rice protein. 

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Ervebo is administered as a single-dose injection. As this is a live virus vaccine, the risk of vaccination in immunocompromised individuals should be weighed against the risk of disease. In addition, transmission of vaccine virus is theoretically possible as vaccine virus RNA has been detected by reverse transcription polymerase chain reaction in blood, saliva, urine, and fluid from skin vesicles of vaccinated adults.

Commenting on the approval, Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research, said, “The FDA’s approval of Ervebo is a major advance in helping to protect against the Zaire ebolavirus as well as advancing US government preparedness efforts. The research approach used to study the effectiveness and safety of this vaccine was precedent-setting during a public health emergency and may help create a model for future studies under similar circumstances.”

According to Merck, Ervebo is expected to be available in the third quarter of 2020. 

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This article originally appeared on MPR