The administration is broadly interpreting legislation approved last year aimed at protecting people and institutions who will begin administering the vaccine this month. The vaccine protects against smallpox but can cause serious reactions in people who get the shot and in people with whom they come into close contact.

Health and Human Services ( news - web sites) Secretary Tommy Thompson outlined the administration's views in a letter to the American Hospital Association, and more detailed guidance is expected this week from the Department of Justice ( news - web sites).

Michael Osterholm, who advises Thompson on bioterrorism issues, said Tuesday that attorneys at HHS and Justice have tried hard to interpret the law so as to offer "the widest umbrella of protection" possible.

This is good news for hospitals and health care workers, who might have been held legally liable to patients and other people who got sick or died from the vaccine. But it means those who are injured have little recourse unless negligence were involved, which would be difficult to prove.

That could deter people from getting vaccinated, said Dr. D.A. Henderson, who chairs a federal advisory committee on bioterrorism that met Tuesday. He said the issue was "potentially a very large problem."

President Bush ( news - web sites) said last month the vaccine would be recommended for health care workers and others who might encounter a highly contagious patient. Vaccinations are expected to begin in at least some states on Jan. 24, when the liability provisions take effect.

The vaccine was not recommended for the general public, given that the disease has been wiped from the Earth without imminent threat of its return. Still, experts fear it could be used in an act of bioterror.

Congress did nothing to provide compensation for people injured by the vaccine, which is made with a live virus capable of causing accidental infections. A federal compensation fund is available for people injured by other, less-dangerous vaccines. But administration officials say they have no plans to propose one for smallpox.

Health care workers vaccinated because of their jobs, who then are stricken, appear to be eligible for workers' compensation in most states, which would compensate them for some of their lost time and health care costs. State programs vary in their details, however, and some will not fully cover the injuries, Thompson adviser Osterholm, a bioterrorism expert at the University of Minnesota, told the advisory panel.

In addition, workers' compensation would not help someone injured after coming into contact with a vaccine, such as a patient in a hospital.

Experts estimate that 15 or more out of every million people being vaccinated for the first time will face life-threatening injuries, and one or two will die. In addition, if the inoculation site is not covered properly, the virus can escape and infect others, causing serious injury or death.

On another matter relating to smallpox, the Advisory Committee on Immunization Practices, which makes recommendations on immunization policies to the Centers for Disease Control and Prevention ( news - web sites), voted 6-0 Tuesday to recommend that adults living with children under 1 year old can be vaccinated for smallpox.

The issue came in a letter from the New York Health Commissioner urging the CDC to exclude adults in that category for fear that infants might develop reactions from the vaccine through contact with vaccinated adults. The committee concluded that chances of serious complications in cases like this were extremely small.

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On the Net: Federal smallpox information: http://www.smallpox.gov.