An Ebola vaccine, already deployed against the often deadly disease in an ongoing outbreak in Congo, is the first approved by the U.S. Food and Drug Administration.

The vaccine, called Ervebo and developed by the pharmaceutical company Merck, underwent testing during the 2014–2016 Ebola outbreak in West Africa and was found to be effective at warding off an infection (SN: 12/22/16).

Approved for those 18 and older, the vaccine prevents disease caused by one species of Ebola virus, Zaire ebolavirus. The FDA’s action, announced December 19, follows in the footsteps of European regulators’ approval in November (SN: 12/16/19). While cases of Ebola in the United States are extremely rare, the FDA considers the vaccine a crucial tool to stop the spread of the disease.

In Congo’s Ebola outbreak, there have been 3,351 cases and 2,211 deaths as of December 18, according to the World Health Organization (SN: 5/21/18). More than 250,000 people have been vaccinated.

Health officials working to control the outbreak have been aided by the vaccine as well as experimental treatments for those already infected (SN: 2/11/19). Two of the four treatments proved effective at preventing death from the disease in a clinical trial conducted during the outbreak (SN: 8/12/19). (One of those treatments is made by Regeneron Pharmaceuticals, a major financial supporter of the Society for Science & the Public, which publishes Science News.)

The number of new cases has been declining, but conditions in the country remain treacherous for those working to bring the outbreak to an end. In late November, armed attackers killed four workers assisting in the outbreak, including a member of a vaccination team.