Update: adverse events following civilian smallpox vaccination--United States, 2003.

During January 24-April 25, 2003, smallpox vaccine was administered to 34,541 civilian health-care and public health workers in 54 jurisdictions to prepare the United States for a possible terrorist attack using smallpox virus. This report updates information on vaccine-associated adverse events among civilians vaccinated since the beginning of the program and among contacts of vaccinees, received by CDC from the Vaccine Adverse Event Reporting System (VAERS) as of April 25.