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Last Updated

29 Mar 2003

Source: Baltimore Sun, March 29, 2003

Researchers seek what links smallpox vaccine, heart ills

Inoculations preceded complaints, deaths; CDC panel offers safeguards

By Erika Niedowski, Sun Staff

The search for causal relationships in medicine is nothing new. Researchers routinely toil in labs, hold clinical trials and pore over statistics, trying to learn whether one thing causes another.

Sometimes, the links they anticipate don't turn up. Other times, two events that appear unrelated wind up being connected after all.

Searching is what federal health officials were doing yesterday as they continued to probe whether smallpox vaccine contributed to heart problems reported by seven health care workers and 10 military personnel inoculated under a Bush administration initiative to prepare for a possible attack using biological weapons.

Three individuals, including a Maryland nurse, suffered fatal heart attacks, and the Centers for Disease Control and Prevention has recommended that people with a known history of coronary disease be temporarily excluded from the vaccination program.

So far, about 26,000 civilian health workers have been inoculated nationwide, including 500 in Maryland. That's far short of the administration's goal of 450,000, but many hospitals and health departments have been hesitant to inoculate large numbers of workers because of unresolved safety and liability issues.

The Defense Department said yesterday that about 300,000 military personnel have been inoculated so far, out of a target of 500,000.

To help determine whether there is a link between the vaccine and the heart ailments, officials are trying to compare the rate of heart problems in the vaccinated population with that of a similar unvaccinated group - based on age, gender and risk factors, among other things.

But even a statistical analysis isn't a foolproof way to connect two events, experts say.

"Is it infallible? The emphatic answer is: By no means is it infallible," said Dr. Donald S. Burke, director of the Center for Immunization Research at the Johns Hopkins University Bloomberg School of Public Health. "Nature sometimes acts in statistically predictable and not-so-statistically predictable ways."

Officials have also been trying to collect tissue specimens from those who have died. Dr. Thomas M. Mack, professor of preventive medicine at the University of Southern California's Keck School of Medicine, said scientists will look for evidence of a viral infection in the heart tissue which might have been caused by the vaccinia virus in the smallpox vaccine.

But even that finding might not provide clear-cut answers.

"Even if they see that, I'm not sure that helps very much," Mack said. He pointed out that small virus particles may routinely show up in the heart tissue of vaccinated individuals - the issue just hasn't been studied so far.

Smallpox vaccine has been associated with life-threatening complications in a small number of patients, but until now, it has not been linked to heart attacks. There is evidence that it may cause heart inflammation, which has been reported in at least 10 military and three civilian recipients.

Many health experts doubt that a link will be found. But at least three states - Florida, New York and Illinois - have temporarily suspended vaccinations until it has been definitively ruled out. The University of Maryland Medical Center also has put on hold its planned vaccination of 40 workers.

The committee that advises the disease control center on immunization practices also took a more conservative approach yesterday. Its members, meeting by telephone, recommended additionally withholding the vaccine from persons who have three known risk factors for heart disease - including diabetes, high blood pressure and high cholesterol.

Concern here has been heightened since a nurse at Peninsula Regional Medical Center in Salisbury suffered a fatal heart attack Sunday, five days after being vaccinated. Two other recent vaccine recipients - a 57-year-old nurse's aide from Florida, Virginia Jorgensen, and an unidentified 55-year-old National Guardsman - died Wednesday after heart attacks. All three had risk factors for heart disease.

Another Maryland woman in her 50s, who has not been identified, suffered a heart attack after vaccination, but officials said she is doing well.

Dr. Robert Edelman, associate director for clinical research at the University of Maryland School of Medicine's Center for Vaccine Development, said the CDC is also likely to investigate whether the vaccinia virus - a less dangerous relative of smallpox - might be exciting an immune response in the heart.

It could be a case of "molecular mimicry," he said, in which molecules of the virus mimic molecules of the heart, and both are attacked as foreign invaders.