Context The United States recently implemented smallpox vaccination of selected military personnel in a national program of preparedness against use of smallpox as a biological. weapon. The resumption of smallpox vaccinations raises important questions regarding implementation and safety. Objective To describe the US military smallpox vaccination program. Design Descriptive study of the vaccination program from its inception on December 13, 2002, through May 28, 2003. Setting US Department of Defense (DoD) fixed and field medical treatment facilities on multiple continents and ships at sea. Subjects US service members and DoD civilian workers eligible for smallpox vaccination. Main Outcome Measures Numbers of vaccinations and rates of vaccination exemptions, symptoms, and adverse events. Data were collected via reports to headquarters and rigorous surveillance for sentinel events. Results In 5.5 months, the DoD administered 450293 smallpox vaccinations (70.5% primary vaccinees and 29.5% revaccinees). In 2 settings, 0.5% and 3.0% of vaccine recipients needed short-term sick leave. Most adverse events occurred at rates below historical rates. One case of encephalitis and 37 cases of acute myopericarditis developed after vaccination; all cases recovered. Among 19461 worker-months of clinical contact, there were no cases of transmission of vaccinia from worker to patient, no cases of eczema vaccinatum or progressive vaccinia, and no attributed deaths. Conclusions Mass smallpox vaccinations can be conducted safely with very low rates of serious adverse events. Program implementation emphasized human factors: careful staff training, contraindication screening, recipient education, and attention to bandaging. Our experience suggests that broad smallpox vaccination programs may be implemented with fewer serious adverse events than previously believed.
