ACAM2000™: The new smallpox vaccine for United States Strategic National Stockpile

Abstract

Smallpox was eradicated more than 30 years ago, but heightened concerns overbioterrorismhave brought smallpox and smallpox vaccination back to the forefront. The previouslylicensed smallpox vaccine in the United States, Dryvax® (Wyeth Laboratories, Inc.), was highlyeffective, but the supply was insufficient to vaccinate the entire current US population. Additionally,Dryvax® had a questionable safety profile since it consisted of a pool of vaccinia virus strainswith varying degrees of virulence, and was grown on the skin of calves, an outdated technique thatposes an unnecessary risk of contamination.The US government has therefore recently supporteddevelopment of an improved live vacciniavirus smallpox vaccine. This initiative has resultedin the development of ACAM2000™ (Acambis, Inc.™), a single plaque-purified vaccinia virusderivative of Dryvax®, aseptically propagated in cell culture. Preclinical and clinical trials reportedin 2008 demonstrated that ACAM2000™ has comparable immunogenicity to that of Dryvax®,and causes a similar frequency of adverse events. Furthermore, like Dryvax®, ACAM2000™vaccination has been shown by careful cardiac screening to result in an unexpectedly high rate ofmyocarditis and pericarditis. ACAM2000™ received US Food and Drug Administration (FDA)approval in August 2007, and replaced Dryvax® for all smallpox vaccinations in February 2008.Currently, over 200 million doses of ACAM2000™ have been produced for the US StrategicNational Stockpile. This review of ACAM2000™ addresses the production, characterization,clinical trials, and adverse events associated with this new smallpox vaccine. © 2010 Nalca and Zumbrun publisher and licensee Dove Medical Press Ltd.