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Cardiac Adverse Events


Cardiac Adverse Events

Myopericarditis is defined as a spectrum of disease caused by inflammation of the myocardium (muscle of the heart wall) and/or the pericardium, which is the sac-like covering surrounding the heart. There is evidence that suggests that some individuals may develop this serious cardiac adverse event within 30 days following the administration of the smallpox vaccine.

SEEK IMMEDIATE MEDICAL ATTENTION if you experience any of the following symptoms:

  • Chest pain
  • Rapid heartbeat
  • Exercise intolerance
  • Shortness of breath

See Algorithm for Treatment Guidelines and Case Definitions.

Is there any difference between the Dryvax Vaccine and ACAM2000 in regard to myopericarditis?

Pre-licensure surveillance with the newer ACAM vaccine revealed occurrence rates similar to Dryvax for myopericarditis.


Cassimatis D, Atwood JE, Engler R, Linz P, Grabenstein J, Vernalis M. (2004) Smallpox vaccination and myopericarditis. JACC;43(9):1503-10.

Eckart R. Love S. Atwood JE, Arness M, Cassimatis D. Campbell C. Boy S. et al. (2004) Incidence and follow-up of inflammatory cardiac complications after smallpox vaccination. JACC;44(1):201-5.

Helle, E.J., Koskenvuo, K., Pikkarainen, J. & Weckstrom, P. (1978). Myocardial complications of immunizations. Annuals of Clinical Research;10:280-287.

Karjalainen J, Heikkila J, Nieminen MS, Jalanko H, Kleemola M, Lapinleimu K, Sahi T. (1983). Etiology of mild acute infectious myocarditis: Relation to clinical features. Acta Medica Scandinavica;213:65-73. 

Last Updated: July 11, 2023
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