Cardiac cases trigger advisory about smallpox vaccination

The Centers for Disease Control and Prevention (CDC, www.cdc.gov) is advising that people diagnosed with heart disease temporarily defer vaccination with smallpox vaccine.

The move comes after 7 American health care workers experienced cardiac problems after being vaccinated, and 2 of them died. Three of the workers had myocardial infarctions and there were 2 cases each of angina and myopericarditis. By the end of March, 25 645 health care workers had been vaccinated as part of US preparations for a potential terrorist attack.

The US government had hoped to vaccinate up to 439 000 doctors, nurses and emergency workers by the end of March, but participation in the voluntary program has been far lower than expected.

Cardiologists say a connection between the vaccine and different types of heart problems is biologically plausible because a smallpox vaccination results in a low-grade infection caused by the vaccinia virus, a relative of smallpox used to produce antibodies against that disease.

The infection can cause widespread inflammation, which in rare cases can involve the heart, even in healthy people; 10 cases have been reported among 350 000 American military recruits who have been given the vaccine.

The CDC says similar cases were reported in the 1960s and '70s when smallpox vaccinations were still common, but reports then did not indicate who might be at higher risk.

The CDC's deferral advisory applies to anyone with a history of cardiomyopathy, previous heart attack or history of angina, or other evidence of coronary artery disease.

Dr. Julie Gerberding, director of the CDC, says a decision about making the temporary deferral permanent will be made as soon as evidence is available. In the meantime, “we believe it is important and necessary to vaccinate health care workers to prepare our nation in the event we have to respond to a smallpox outbreak.” — Patrick Sullivan, CMAJ