The Food and Drug Administration announced Thursday the approval of a vaccine to prevent the deadly Ebola virus.

The vaccine, called Ervebo, is the first such drug to gain FDA approval in the United States. Ervebo was approved by the European Commission in November.

In a study conducted in West Africa during the 2014-16 Ebola outbreak, the vaccine was found to be 100 percent effective in preventing the deadly disease.

The vaccine, made by Merck & Co., is administered as a single dose injection. It is approved for people ages 18 and up.

The Ebola virus is spread through contact with blood and other bodily fluids. It can cause massive internal bleeding, vomiting, diarrhea and death. An outbreak often starts with a "spillover event," meaning the virus is transmitted from an animal to a human. Then, the virus can spread from person to person.

There isn't much risk of Ebola spreading in the U.S.; the only cases seen here have been the result of infections acquired by patients in other countries who then traveled to the U.S., or health care workers who became ill while treating Ebola patients abroad, the FDA says.

“While the risk of Ebola virus disease in the U.S. remains low, the U.S. government remains deeply committed to fighting devastating Ebola outbreaks in Africa, including the current outbreak in the Democratic Republic of the Congo,” Anna Abram, the FDA's deputy commissioner for policy, legislation and international affairs, said in a statement Thursday.

The outbreak in the DRC is the second largest Ebola epidemic on record, according to the World Health Organization, with a total of 3,351 cases and 2,221 deaths.

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