Maryland forged ahead with a slightly modified smallpox vaccination campaign yesterday after two recently inoculated women in the state suffered heart attacks - one of them fatal.
Federal officials continued to probe a possible link between the vaccine and heart problems reported in seven inoculated health workers nationwide.
Although several experts said it is unlikely the vaccine contributed to the heart ailments, the University of Maryland Medical Center was debating whether to delay its planned vaccination of 40 employees until a connection has been definitively ruled out.
"This could be chance. But you don't want to assume that it's chance until you really know," said Dr. Harold C. Standiford, the hospital's medical director of infection control.
A nurse at Peninsula Regional Medical Center in Salisbury who was vaccinated March 18 died of a heart attack five days later in Virginia, according to Lucy Caldwell, a Virginia Department of Health spokeswoman. Officials have refused to identify the victim, who was in her 50s, but said further tests are under way.
Another of the three heart attack victims identified Monday by federal health officials also was from Maryland, said Dr. Julie Casani, head of the state's Office of Public Health Preparedness. She said that the woman was "doing well" but refused to release further information.
Dr. Judith A. Sensenbrenner, the health officer in Wicomico County, said yesterday that the vaccine does not appear to have contributed to the Peninsula nurse's death.
Smallpox vaccinations were routine for children during most of last century but they were discontinued after the disease was eradicated worldwide in 1980.
The latest vaccinations are part of a Bush administration initiative to inoculate nearly half a million health workers who could then respond to an attack by terrorists using the smallpox virus. But far fewer workers have volunteered because of safety concerns - only 25,645 nationwide as of last week, including about 500 in Maryland.
After receiving seven reports of heart problems among the vaccinated health workers last week, the Centers for Disease Control and Prevention revised its screening guidelines to temporarily exclude those with known heart disease.
The three patients who had heart attacks and two who suffered chest pains after vaccination all exhibited classic risk factors such as obesity, high blood pressure, diabetes or tobacco use, the CDC said.
The smallpox vaccine, made from a live virus related to smallpox, has been known to produce potentially serious complications in a tiny proportion of recipients. But heart problems have not been among them.
Cases of heart inflammation among those inoculated were reported in the 1960s and 1970s, but those reports contained no information about who might be at greater risk for post-vaccination heart trouble.
The chief of infectious diseases at the Johns Hopkins University School of Medicine, Dr. John G. Bartlett, says he doubts that a link will be established.
"It does not make sense to me that a vaccine - any vaccine - would cause a heart attack," he said.
Heart attacks occur when arteries in the heart become blocked, usually over time as plaque builds up. Also, the type of chronic inflammation linked to heart attacks is not the kind that the vaccine might cause, he said.
"I don't think there's a link, but I think the CDC is doing the right thing," Bartlett said. "They just need to be very cautious about who gets this vaccine."
Dr. Robert Edelman, associate director for clinical research at the University of Maryland School of Medicine's Center for Vaccine Development, says he knows of no relationship between the vaccine and heart problems.
But he theorized that the vaccine could tip the scales for people on their way to a heart attack if the live virus caused a high fever, forcing the heart to work harder. A partial blockage of the coronary arteries would make it harder for enough oxygen to get to the heart, he said, possibly leading to a heart attack.
"That's all theoretical," he added.
Even as the vaccination of Maryland health workers proceeds under the new CDC guidelines, some have concerns. George Paul, president of the 2,000-member Maryland Nurses Association, said that shortly after the program began last month, his group recommended that members not be vaccinated because of unresolved liability issues.
"There were a small number of incidents of people having complications, and that had some people concerned about the risks," he said.
But Phyllis Brodsky, 66, a Berlin resident and president of the association's Eastern Shore chapter, said she plans to be inoculated when she takes a disaster training course next month.
"My own feeling is that there's not a great risk to taking this vaccine, and if there's a disaster I want to be able to respond," she said.
Sun staff writers Chris Guy and Dennis O'Brien contributed to this article.