Questions & Answers
Smallpox - Vaccine - Cardiac Related Reactions
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Heart-Related Problems After Smallpox Vaccination

  1. What has the Department of Defense (DoD) seen in terms of heart inflammation after smallpox vaccination?

    The Department of Defense reported its first case of inflammation in or around the heart (myopericarditis) after smallpox vaccination in early February 2003. As of January 2008, DoD has identified 161 cases of acute myocarditis and/or pericarditis among 1.4M smallpox vaccinees, with symptoms appearing 7 to 19 days after vaccination. These people had clinical conditions that varied from mild to moderate; the condition was severe in two cases.

    Most cases occurred among those receiving smallpox vaccinations for the first time. Most cases occurred among men.

    The health of our people is foremost in our priorities. These cases were followed carefully to evaluate their recovery, at 27 hospitals in 21 states and several countries overseas. Detailed follow-up cardiac testing is available in 46 cases: all had normal electrocardiograms (EKGs), echocardiograms ("echos") and normal treadmill test results. Based on our data and European experience, we have reason to believe these people should recover and remain well.

  2. What is the difference between myopericarditis, myocarditis, and pericarditis?
    Myocarditis is an inflammation of heart muscle tissue (the myocardium). Pericarditis is an inflammation of the sac surrounding the heart (the pericardium). When both conditions occur at the same time or to group both categories together, it is called myopericarditis.

  3. Is there a relationship between the reported heart attacks and DoD's findings of myocarditis and/or pericarditis in smallpox vaccinees?
    Myocarditis and heart attacks are different diseases. Myocarditis involves inflammation of the heart muscle. Heart attacks are different, in that they involve problems with heart rhythm or blood vessels in the heart. At present, there is no evidence of a link between myocarditis and heart attacks. But DoD continues to investigate any possibilities of a relationship between vaccination and an adverse event.

  4. How does smallpox vaccine cause myocarditis or pericarditis?
    The precise cause is unknown; however, a reasonable theory is that the vaccinia virus in smallpox vaccine gets into the blood stream and then causes inflammation in the heart tissue.

  5. Was the finding of myopericarditis a surprise to DoD officials? Is this a new or previously unknown reaction?
    Because rare cases of myopericarditis have been reported previously following smallpox vaccination, notably in a study of Finnish military recruits in the 1980s, DoD was watching for the occurrence of myocarditis and was not surprised. In Finland, 1 in 10,000 vaccinees developed myopericarditis.

  6. How was the myocarditis or pericarditis diagnosed in service members?
    The patients with myocarditis and/or pericarditis sought medical care after developing chest pain. Blood tests showed that they had elevated levels of enzymes (such as CKMB or troponin), suggesting myocarditis or pericarditis. They had temporary changes in ECG (electrocardiogram) and/or echo-cardiogram readings.