WASHINGTON (AFPN) -- Department of Defense officials are taking a watchful approach to the department's smallpox vaccination program after the Centers for Disease Control and Prevention in Atlanta reported investigating whether a sequence of cardiac deaths was associated with the vaccine.

Government officials have suggested that anyone with certain heart-related risk factors not take the vaccine. They continue to examine several suspected cases, including that of a 55-year-old National guardsman who died of a heart attack five days after receiving the vaccine.

Following the CDC's recommendation, Col. John Grabenstein, deputy director for military vaccines for the Army's surgeon general, said the Defense Department is revising its policy for some 500,000 military members whom it plans to vaccinate against smallpox.

The military has medically screened vaccine recipients since the program's beginning, Grabenstein said. He said officials would now take an even closer look at risk factors such as tobacco use, high blood pressure, high cholesterol, diabetes and family history of heart disease before giving the vaccine.

"People with three or more of those conditions would be exempted," he said. Grabenstein cautioned anyone -- vaccinated or not -- to seek health care if they experience chest pain or shortness of breath with exertion.

Military members receiving the vaccine are those deployed or deploying to a U.S. Central Command area of operation; those who would go into a smallpox outbreak area to help control the disease; and health care workers at DOD hospitals and clinics who would treat smallpox patients.

Grabenstein said there is no plan to vaccinate everyone in the military at this time. "It's a pretty focused and targeted program," he said.

Even with the public concern over the safety of vaccine, he said the recent deaths seem to be in proportion with usual rates of death.

"The evidence that we have so far shows that these are not linked in a cause and effect way," Grabenstein explained. "The deaths seem to be just the natural level of heart attacks that occur among unvaccinated people. But the investigation is not finished, and to be on the safe side, this extra precaution is being taken."

More than 350,000 servicemembers have been vaccinated, with "the expected number of post-vaccination symptoms and few serious reactions," he said.

"Lots of people had itching at the vaccination site, swollen lymph nodes under the arms, which are fairly common," Grabenstein said. "In terms of serious reactions, we've had few, in fact fewer than we would have expected looking at the historical figures. We're pleased with the success of the program."

On Dec. 13, President Bush announced a nationwide smallpox vaccination plan out of concern that bioterrorists could use the germ that causes the smallpox disease as an agent to attack the United States. Although smallpox was eradiated in 1980, the germ was kept in two laboratories in the United States and the former Soviet Union for study. Whether the germ is in other locations is unknown.