The US Centers for Disease Control and Prevention (CDC) kept a stockpile of the drug to use in case of emergency. In 2003 this supply helped contain an outbreak of monkeypox in the United States. In February 2008 the CDC disposed of the last of its 12 million doses of Dryvax. Its supply is being replaced by ACAM2000, a more modern product manufactured in laboratories by Acambis
Dryvax is a live-virus preparation of vaccinia prepared from calf lymph. Trace amounts of the following antibiotics (added during processing) may be present: neomycin sulfate, chlortetracycline hydrochloride, polymyxin B sulfate, and dihydrostreptomycin sulfate.