Fatal heart attacks rock smallpox vaccine efforts

Link could damage national campaign

(Editor’s note: A 55-year-old man in the National Guard suffered a fatal heart attack following smallpox vaccination as this issue of Occupational Health Management went to press. That case is not reflected in the following seven cases described in the story below, which all occurred in hospital or public health workers.)

Two fatal heart attacks following smallpox vaccination of health care workers threaten to further derail a struggling government immunization program already suffering from a striking lack of hospital participation.

Though a direct cause and effect has yet to be established in an ongoing investigation, the reports do not bode well for a program that has vaccinated only about 5% of the 500,000 hospital workers it originally projected.

A nurse at Peninsula Regional Medical Center in Salisbury, MD, died of a heart attack on March 23, 2003, five days after being vaccinated. She was reportedly in her 50s. On March 26, 2003, a 57-year-old health care worker in Florida died 10 days after suffering a heart attack that occurred a week after being vaccinated for smallpox.

Those cases and reports of five other heart-related adverse effects among vaccinees prompted the Centers for Disease Control and Prevention (CDC) to declare a history of heart disease as a new contraindication for receipt of smallpox vaccine. Health care workers should not receive smallpox vaccine if they have a history or a diagnosis of coronary artery disease, myocardial disease such as angina, heart attack, congestive heart failure, or any kind of cardiomyopathy. Health care workers who already have been vaccinated should immediately consult a physician if they have any symptoms of heart disease, such as shortness of breath or chest pain, the CDC advises.

There is some concern that the effect on the program may ripple out beyond the specifics of that contraindication. The new heart disease contraindication may give pause to workers — or their personal physicians — with any peripheral concerns about, for example, diabetes or blood pressure, says William Schaffner, MD, chairman of the department of preventive medicine at Vanderbilt University Medical Center. Beyond that — even if the deaths are later ruled entirely unrelated to the smallpox vaccine — a certain amount of "re-education" will be necessary to reassure health care workers about the program, he adds.

"Clearly, if we look at all known risk factors for coronary artery disease, we would potentially get to very, very large numbers of the population, and it would, in essence, be very difficult to enhance our preparedness," concedes Walter Orenstein, MD, chief of the CDC national immunization program. "What we’ve tried to do is pick out people with the very highest risk factors, in the absence at this point, of any known causal relationship."

Indeed, the CDC is determined to forge on, particularly with the threat of bioterrorism related to the war in Iraq.

"Certainly, we are a time in the history of our country where the potential for terrorism has probably never been higher," says Julie Gerberding, MD, MPH, director of the CDC. "And we recognize that we must continue to be prepared to deal with a threat of smallpox in our nation. We are going to continue the program. But we’re also going to continue the program with the caveat that safety still is a high priority for us. And every time we put something on the list of medical conditions that constitutes a basis for deferral, we recognize that it does decrease, to some extent, the population of people who are willing to volunteer. But it’s a balance. And I think, again, we want to err on the side of safety."

Two deaths after 25,000 vaccinated

The CDC discovered the seven cases of heart-related problems among the 25,645 health care and public health workers who have been vaccinated in the civilian program. The seven cases include three cases of myocardial infarction (heart attack), two of which resulted in the aforementioned deaths; two cases of angina (chest pain); and two cases of myopericarditis (inflammation of the heart muscle or sac surrounding the heart).

Issuing the contraindication is a clear case of erring on the side of caution, because a definitive link to smallpox vaccination has not been established in any of the cases.

"I think the first hypothesis is that this is not causally related," Gerberding says. "That’s the null hypothesis in this case that we’re working from. But I think there is also at least the biological plausibility that when you have a viral infection — which is basically what happens when you issue the vaccine — that there could be inflammatory response that in some unidentified way exacerbates pre-existing coronary artery disease or inflammation."

The CDC convened a panel of expert cardiologists and immunologists to review the cases to determine if the problems are vaccine-related. Investigators will also look at comparable populations in other studies to assess the incidence of cardiac problems in unvaccinated people. The CDC also is trying to determine if the heart problems may occur at a higher rate in females, which comprise the majority of health care workers being vaccinated for smallpox.

"The five patients who have had the coronary artery disease related complications — the three with MI, and the two with angina — all have very clear, defined risk factors for coronary artery disease," she says. "That is known in their medical history, and these are people who would medically be considered to be at perhaps increased risk of these conditions, based on their past medical history."

Smallpox vaccination and cardiac problems have not been linked in the historical smallpox literature, but more older people are being vaccinated now than during the childhood immunization programs prior to smallpox eradication. The three workers who had heart attacks were all women in their 50s. In all seven cases, the time lag between vaccination and cardiac problems varied from five to 17 days. No adverse reactions were noted at the time of vaccination.

"We don’t have a lot of epidemiologic or scientific information about the relationship between vaccine and cardiac illness in persons who are older and who were not involved in the childhood immunization program where we had the most experience in the ’60s." Gerberding says.

The problem is that older staffers who have been previously immunized have been considered at lower risk of adverse effects. Might the CDC begin discouraging senior staff to be inoculated for smallpox?

"I don’t think that we are prepared to take that step at this point in time," she says. "We’ll defer to the expert input that we anticipate receiving from people who are the most credible in the world of cardiac risk assessment."