Myocarditis, Pericarditis, and Dilated Cardiomyopathy after Smallpox Vaccination among Civilians in the United States, January–October 2003

Abstract

Myocarditis was reported after smallpox vaccination in Europe and Australia, but no association had been reported with the US vaccine. We conducted surveillance to describe and determine the frequency of myocarditis and/or pericarditis (myo/pericarditis) among civilians vaccinated during the US smallpox vaccination program between January and October 2003. We developed surveillance case definitions for myocarditis, pericarditis, and dilated cardiomyopathy after smallpox vaccination. We identified 21 myo/pericarditis cases among 37,901 vaccinees (5.5 per 10,000); 18 (86%) were revacinees, 14 (67%) were women, and the median age was 48 years (range, 25-70 years). The median time from vaccination to onset of symptoms was 11 days (range, 2-42 days). Myo/pericarditis severity was mild, with no fatalities, although 9 patients (43%) were hospitalized. Three additional vaccinees were found to have dilated cardiomyopathy, recognized within 3 months after vaccination. We describe an association between smallpox vaccination, using the US vaccinia strain, and myo/pericarditis among civilians.

Economics of Cardiac Adverse Events after Smallpox Vaccination: Lessons from the 2003 US Vaccination Program

“…Finally, it is likely that not all CAEs are causally associated with vaccinia. In a conservative scenario, and considering that MP has been the only CAE associated with the US smallpox vaccine [7,12], only the health and economic burden on vaccinees with MP could be attributed to smallpox vaccine. A baseline adjustment with the incidence of cardiovascular diseases in absence of smallpox vaccination may reduce the true number of postvaccinia CAEs and costs.…”

Vaccination against Smallpox in the Posteradication Era

“…Systematic observations of the military and civilian programs, reported here and elsewhere, document that, with due diligence to vaccinee education and postvaccination surveillance and follow-up, adverse events historically recognized in association with smallpox vaccination can be minimized. Enhanced surveillance systems also provided systematic observations that detected vaccine-associated adverse events that were previously unrecognized or underappreciated [19,22]. Observations from the development, implementation, management, and analysis of compensation programs, vaccine-delivery programs, and safety-monitoring systems during the 2003 National Smallpox Pre-Event Vaccination Program, reported in this supplement and elsewhere, provide valuable lessons and a basis for streamlined and otherwise improved function as vaccination against smallpox proceeds into the future.…”

“…Reports of serious adverse events included 21 cases of myocarditis and/or pericarditis ("myo/ pericarditis") and 10 reports of ischemic cardiac events [7,8,[18][19][20]. The remaining articles in this supplement describe observations focused on specific aspects of safety monitoring during the 2003-2004 National Smallpox Pre-Event Vaccination Program.…”

“…These observations raised alarm and led to urgent and vigorous investigation, details of which are reported in this supplement by Swerdlow et al [18], Morgan et al [19], Sniadack et al [20], Neff et al [8], and Clark and Levin [10]. Investigations of ischemic cardiac events provided reassurance that these events were likely not causally associated with smallpox vaccination [18,21].…”

“…In contrast, Department of Defense observations clearly documented a statistically increased risk of myocarditis of unclear significance among military personnel who had recently received the smallpox vaccine for the first time [22]. Morgan et al [19] report the outcome of an investigation of persons who developed myocarditis, pericarditis, or advanced cardiomyopathy after receipt of smallpox vaccine in the civilian program and provide detailed descriptions of clinical cases. The report by Sniadack et al [20] provides the only published follow-up information available on the clinical status of civilian vaccinees who reported possible cardiac adverse events after smallpox vaccination.…”