September 2004, the Food and Drug Administration lifted the clinical hold on enrollment in the ACAM2000 trials and concurred with Acambis that enrollment could be closed and analysis of the data could begin. Acambis undertook 12-month followup of affected study subjects.

Both DoD and CDC conducted followup of vaccinees with myo/pericarditis (Mootrey, 2003). Research on myo/pericarditis is needed, and efforts are already in progress. In July 2004, the National Institutes of Health provided funding for research on the effect of smallpox vaccine on cardiac cells in mice (Roos, 2004b).

Vaccination Program Safety Profile

In the weeks surrounding the beginning of the program, health care and public health organizations described their unease regarding specific safety issues related to the vaccination program. Although the program was voluntary, the potential of inadvertent transmission of vaccinia virus meant that adults and children who had neither consented to vaccination nor been screened for contraindications could become infected and face the risk of severe adverse events or even death (AAP, 2003). Some organizations also feared that the pace of the vaccination program could make it difficult to arrange staff schedules to provide time for leave or furlough in order to ensure patient safety (Burstein, 2002; Peterson, 2002; Schulman, 2002; Baker, 2003).

Reintroducing the smallpox vaccine in the absence of the disease required special attention to safety, including screening for contraindications and preventing the inadvertent transmission of vaccinia virus to contacts because the risk-benefit ratio was less clear in the absence of naturally occurring smallpox. CDC and its state and local counterparts worked to ensure safety at every step before, during, and after vaccination. CDC made every effort to develop effective and efficient screening methods and guidelines for pre-event smallpox vaccination clinics. In response to the present committee’s recommendations, CDC developed an information sheet for contacts of vaccinees and modified the Pre-Event Vaccination System to document active surveillance of vaccine-related adverse events that required hospitalization or outpatient care, contraindications to vaccination among volunteers or their household contacts not identified before vaccination, and vaccinia-virus transmission to contacts (CDC, 2003e; IOM, 2003a). Volunteers were given multiple opportunities to learn about the vaccine and vaccination and to opt out if they determined that they were unable or unwilling to be vaccinated, and a thorough informed consent process was put into place.

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