ATLANTA (USA TODAY) -- The future of the government's smallpox-preparedness program may be decided not by the White House or the Centers for Disease Control and Prevention but by the nurses, doctors and others who are not lining up for voluntary vaccinations.

Even before an expert panel advised last week against expanding the vaccine program beyond the first phase, the program had slowed to about 100 vaccinations a week. Nearly 38,000 medical and public health workers have been immunized, far fewer than the 450,000 initially expected in the program's first phase. In the next phase, the vaccine is to be offered to police, firefighters and emergency workers, potentially 10 million people.

Thursday's recommendation not to move forward was made by the Advisory Committee on Immunization Practices, which provides advice on vaccines to the CDC. The committee cited concerns about "new and unanticipated safety concerns," specifically nearly two dozen cases of myocarditis, a potentially life-threatening inflammation of the heart muscle, and pericarditis, a less dangerous inflammation of the heart lining, that have occurred among recently vaccinated people in the civilian part of the program. The military has seen nearly 50 such cases among the more than 454,000 military personnel vaccinated since December.

Many medical experts have not been convinced that the unknown risk of a smallpox attack is balanced by the known risk of the vaccine itself, which contains a live virus similar to smallpox that can cause life-threatening side effects. Offering it to medically trained people within a medical setting seemed a manageable risk to many on the advisory committee, but widening the program dramatically did not.

"The committee has believed from the beginning that we need to put safety above and beyond all other concerns," said committee chairman John Modlin, a professor at Dartmouth Medical School. A pause in the smallpox program, he said, "will allow us to buy some time and better understand both sides of the equation, the safety and the threat."

CDC director Julie Gerberding said in a briefing that there is no indication that the risk of smallpox has changed since December, when President Bush announced the policy in preparation for a possible bioterrorist attack. "We have made a giant step forward in our preparedness," she said, "but we are not done yet."

The CDC will balance the committee's advice "with the other priorities that are necessary to make a sound public health decision," Gerberding said.

Florida already has moved into the second phase of the program, and 124 emergency workers have been vaccinated. No slowdown of the program is planned, health department spokeswoman Lindsay Hodges said. The state "is committed to this, as both an effort to deter any attack or to react in the face of an attack," she said.

But in Texas, a decision to wait before moving into Phase 2 "will play well," health department spokesman Doug McBride said. "There has been concern expressed by state officials for several months about the wisdom of going straight from Phase 1 into Phase 2 without the time to look at safety considerations, to assess, to gear up and plan it."

Copyright 2003 USA TODAY, a division of Gannett Co. Inc.