The National Institute of Allergy and Infectious Diseases said an experimental Ebola vaccine is being processed at a facility in Frederick.
The Frederick News-Post reported that the vaccine is a joint project between the federal agency and GlaxoSmithKline.
Agency spokeswoman Jennifer Routh said the active ingredients are sent to the plant on Geoffrey Way, where they are put into vials and prepared for use.
Routh said the vaccine is for use in clinical trials at the National Institutes of Health in Bethesda, about 30 miles away. She said the trials involving human subjects began last month.
Routh said the vaccine includes parts of two Ebola subspecies called Zaire and Sudan. The World Health Organization said the Zaire subspecies is causing most of the current outbreak in West Africa.