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Getting to the Heart of the Smallpox Vaccination Program

Following vaccination, 30 unanticipated cardiac events have occurred, including ischemia (believed unrelated to vaccination) and myopericarditis (more likely related).

Phase one of the CDC and defense department pre-event smallpox program was designed to vaccinate sufficient numbers of hospital-based healthcare workers (HCWs) to enable immediate care for up to 5 cases per hospital for up to 5 days. Through May 9, 2003, a total of 36,217 HCWs were vaccinated. This report documents 30 unexpected cardiac events that occurred within 42 days of vaccination.

Cardiac events included a myopericarditis (MP) syndrome that affected 21 HCWs and ischemic events that affected 9. The MP syndrome was characterized in 6 patients by pericarditis and in 15 by myocarditis (chest pain and ECG changes consistent with inflammation); 7 of these also had dysrhythmias (atrial fibrillation, atrial ectopy, paroxysmal atrial fibrillation, or premature ventricular contractions). Ninety percent of MP-syndrome patients were re-vaccinees, and 71% were female; median age was 48. All patients with MP syndrome recovered. Six of the 9 patients with ischemia had myocardial infarctions (MIs); 3 had angina. At least 8 of these HCWs were re-vaccinees, and 33% were female; median age was 57. Two female patients who had MIs died.

Comment: The current rate of MP syndrome (1:1,700) is higher than that noted when smallpox vaccination was routine and higher than the rate among military personnel (1:12,000), perhaps because HCWs tend to be older. Although the number of post-vaccination MIs (5) is higher than that predicted in a similar, unvaccinated population (2), it is not greater than the 95% predictive interval and thus may not be related to vaccination. These cardiac events have led to expanded exclusion criteria for vaccination and have helped to diminish the number of vaccination volunteers.

— Stephen G. Baum, MD

Published in Journal Watch Infectious Diseases June 20, 2003

Citation(s):

Update: Cardiac-related events during the civilian smallpox vaccination program--United States, 2003. MMWR Morb Mortal Wkly Rep 2003 May 30; 52:492-6.

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