More than 50 people have had heart inflammation after getting the smallpox vaccine, and a recipient has suffered a brain illness, health officials said Thursday.

The possible side effects are in addition to three heart attack deaths reported in March.

Some 24 civilians have had inflammation of the heart or surrounding membranes, the Atlanta-based Centers for Disease Control and Prevention said. Another 27 members of the military have had the conditions, according to the Defense Department.

More than 36,000 civilians and 430,000 military personnel have been vaccinated since the program started in January in anticipation of a potential bioterrorism attack.

Some side effects were expected, but the heart problems have taken some doctors by surprise. Few cardiac events were recorded when smallpox vaccination was routine in the 1950s and '60s.

Most of those vaccinated decades ago were children, and the two main tests for detecting heart disease today hadn't been developed. People getting inoculated now are adults, many of whom have heart problems or are at risk for cardiac disease.

``I think we just missed these before,'' said Dr. J. Michael Lane, former chief of the CDC's smallpox eradication program. ``We didn't have the technology to find them.''

But some of the heart complications may be unrelated to the vaccine, Lane said.

In early April, the CDC advised against vaccination for people with heart disease or at least three risk factors, including high blood pressure, high cholesterol, diabetes, smoking and heart disease at age 50 in close relatives.

The 38-year-old man with the brain illness had respiratory problems 10 days after getting the vaccine in April. He was hospitalized for a week. The day after being released, he became agitated and confused, and a few days later he had a seizure.

He was diagnosed with encephalomyelitis, inflammation of the brain and spinal cord.

The man, who remains mildly confused, is a heavy smoker who tested positive for marijuana and tranquilizers. More tests are being performed to see if his condition may have been caused by something other than the inoculation.

The federal government's campaign to vaccinate a half-million health care workers against smallpox has fallen far short, with 36,600 workers covered as of mid-May.

A second phase calls for inoculating 2-3 million ``first responders'': police officers, firefighters and paramedics. Some states, such as Florida, have launched a broader effort.

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