A 55-year-old National Guardsman died this week from a heart attack, the Pentagon said Friday, in the third such death that followed a smallpox vaccination.

The Defense Department is joining the Centers for Disease Control and Prevention in deferring people with heart disease from being given the vaccinations until a possible relationship can be investigated, said Dr. Bill Winkenwerder, assistant secretary of defense for health affairs.

In Florida, where a health worker died this week after a heart attack, officials temporarily stopped vaccinations so they could re-screen people who had volunteered for the shots and eliminate any with heart problems. New York put its program on hold early this week.

On Friday, a federal advisory committee was considering how many people should be excluded from the vaccination effort. One option being considered would exclude anyone over age 50.

At the Pentagon, Winkenwerder said the soldier who died also smoked and had high cholesterol. An autopsy showed that he had had coronary disease.

Because of those findings, Winkenwerder said, it appears unlikely that the vaccine caused the man's death.

The man suffered the heart attack Tuesday and died Wednesday, Winkenwerder said.

CDC issued its warning after a Maryland nurse died of a heart attack Sunday and a Florida health worker died of a heart attack later in the week. More minor cardiac problems were seen in 15 others who had been inoculated, including 10 people in the military and seven civilians.

The smallpox vaccine has never been associated with heart trouble, but CDC officials said Thursday there was some evidence the vaccine is playing a role in heart inflammation.

Winkenwerder said the military has had few serious side effects from the vaccine program. Two cases of encephalitis had been reported previously. So far about 300,000 military personnel have been vaccinated, he said, with the aim of reaching about 500,000.

He said there have been about 10 cases of heart inflammation reported in those vaccinated, but none was severe. Some people have been hospitalized for one to three days and then returned to duty. Those cases involved people in their 20s and 30s, he said.