Georgia starts its first round of smallpox vaccinations today amid a growing national backlash that threatens to cut the number of health workers protected against bioterrorist attack by half or more.

With five of seven Atlanta trauma centers declining to participate, fewer than 75 hospital employees and state health workers are expected to receive the vaccine. The turnout mirrors reactions across the country: Key hospitals and medical schools have withdrawn from the plan; unions representing health care workers have urged members not to participate; and health organizations have urged that vaccinations be suspended until Congress creates protections for recipients.

With opposition accelerating, two Senate committees have called hearings this week on smallpox vaccination. At the first Wednesday, state and local health officials said the plan is costing more than predicted and is draining resources from other important public health programs.

"Staff members who worked in communicable disease control are now focusing exclusively on smallpox," said Patrick Libbey, executive director of the National Association of County and City Health Officials, "[compromising] our ability to prevent and respond to influenza, childhood diseases, West Nile virus, contaminated drinking water, food-borne illness and chronic diseases."

As of Wednesday night, 38 states, Los Angeles and Chicago had asked the Centers for Disease Control and Prevention to send 205,700 doses of vaccine, making it unlikely the administration will achieve its goal of 500,000 vaccinations in 50 states plus several cities and territories.

Jurisdictions that have begun to vaccinate are moving cautiously. Los Angeles -- which plans to vaccinate 9,200 health workers -- began its campaign Friday by giving the vaccine to 60 workers; county officials said they will proceed slowly to ensure safety. In Connecticut, which on Friday became the first state to vaccinate, only four workers showed up instead of the 20 expected. New York City, which a year ago voiced some of the first and most aggressive demands for vaccination, has not ordered its vaccine from the Atlanta-based CDC.

The newfound caution about vaccination brings other states and cities into line with Georgia, which has always planned a conservative campaign of no more than 400 vaccinations. Today's shots, being given at the North DeKalb Health Center, are the first of four phases the state plans to roll out over four months, taking time between vaccinations to gather data on bad reactions to the shots.

Fears of the vaccine are based on its high rate of side effects: For every 1 million vaccinations, according to CDC studies, there will be one to two deaths, 15 to 52 life-threatening reactions, and up to 1,000 milder reactions that can nonetheless have serious consequences.

"We are all struggling to find the right balance here between risk and preparedness and expediency," Dr. Julie Gerberding, the CDC's director, said at the Senate hearing, adding that safety of health workers and patients "is the highest imperative for us."

There are no guarantees that workers made sick by the vaccine will be compensated for medical costs, disability or lost wages. In a 34-state survey, the Association of State and Territorial Health Officials found that almost every state would have some difficulty covering vaccine injuries with workers' compensation laws.

The American Federation of State, County and Municipal Employees, which represents 350,000 health care workers, warned Wednesday that contract employees in hospitals, who range from janitors to doctors in small practice groups, may not be covered by health insurance if the vaccine makes them ill.

Calls for a slowdown in vaccinations have come from the Service Employees International Union, the American Federation of State, County and Municipal Employees, the American Nurses Association, and the American Public Health Association among other groups.

About 100 hospitals have recommended that workers not volunteer.

"People who volunteer to take the vaccine are taking a risk to protect us, and we should protect them in turn," said Dr. Georges Benjamin, executive director of the American Public Health Association, which has asked Congress to create a compensation fund for vaccine recipients. "It's the right thing to do."