The US government will purchase up to 1.13 million doses of a pair of Ebola vaccines and treatments to keep on hand in the event of another outbreak, the Biomedical Advanced Research and Development Authority said yesterday.

BARDA, part of the Department of Health and Human Services, will spend $170 million to stockpile two vaccines and two treatments. While the authority can purchase the drugs, none have been approved for use by the Food and Drug Administration. According to Reuters, BARDA will help each manufacturer “validate its manufacturing processes and make final preparations needed to apply for FDA approval,” but has the authority to keep a stockpile of the drugs on hand, even if they aren’t approved.

The authority is purchasing the drugs through the Project BioShield Act, a 2004 law designed to stockpile treatments for biological, chemical, nuclear incidents for the country’s civilian population. The purchase comes after the West African Ebola Outbreak infected 28,616 people and killed 11,310 between 2013 and 2016. Four cases were reported in the United States, with one dying as a result.

The outbreak prompted numerous efforts to find treatments for the often-fatal disease, and a 2016 trial of a drug manufactured by Merck and Co. in Guinea and Sierra Leone yielded highly effective results. Other efforts are underway as well. Earlier this week, the National Institutes of Health granted Thomas Jefferson University $2.6 million to develop a new vaccine for the Ebola, Sudan, Marburg, and Lassa fever viruses.

The Ebola virus first appeared in Central Africa in the 1970s and is thought to be transmitted to humans through animal contact. Those infected experience fever, headaches, and muscle pain, followed by vomiting, diarrhea, and in some cases, internal and external bleeding. Since its discovery, the disease periodically surfaced in Central Africa in small outbreaks. In 2013, the illness appeared in West Africa, where it quickly spread throughout 10 countries and took months to bring under control. Earlier this summer, four people were killed during a small outbreak of the disease in the Democratic Republic of the Congo. The outbreak was brought to an end in 42 days without the use of the new vaccines or treatments.