Modern factors may boost smallpox vaccine risk. (Infection of Secondary Contacts).

DENVER -- "Should I get vaccinated for smallpox?"

Physicians report that an increasing number of patients are asking this question since the U.S. government launched a drive last year to vaccinate up to 450,000 health care workers and 10 million emergency workers for smallpox, Dr. Melvin Berger said at the annual meeting of the American Academy of Allergy, Asthma, and Immunology.

The answer may paint a somewhat frightening picture of potentially serious or even fatal side effects of smallpox vaccination--one of the main reasons why only 25,000 nonmilitary persons have been vaccinated since last year, and why 10 states have suspended smallpox vaccinations altogether.

Earlier this year, the Centers for Disease Control and Prevention revised eligibility guidelines for the smallpox vaccine program after two health care workers and a National Guardsman died of heart attacks following vaccination, The program now excludes persons with heart disease or at least three of four cardiovascular risk factors: high blood pressure, diabetes, high cholesterol, and smoking.

Additional revisions to CDC's smallpox vaccine eligibility guidelines are likely with increasing reports of adverse events, said Dr. Berger, professor of pediatrics and pathology at Case Western Reserve University, Cleveland, and member of the U.S. Army Reserve.

U.S. data from 14 million smallpox vaccinations in 1963 showed that most of the vaccine reactions occurred in persons who were vaccinated for the first time, 4% occurred in persons who were revaccinated, and 20% occurred in persons who came into contact with vaccinees. At the time, nearly all of those who were revaccinated were first vaccinated only a few years earlier, "not like the decades-long gap we have today" between smallpox vaccinations, Dr. Berger said. "We anticipate adverse events in revaccinations may be higher than before."

Infection of secondary contacts also is "a big concern," he added. The 20% of vaccine-related adverse events reported in secondary contacts in 1963 occurred in an era "when you were coming home to a household where everyone is vaccinated. Today, no one is immunized," making ...