More than 1,800 health care workers in Baltimore will be vaccinated against the smallpox disease under the first phase of a plan to prepare for a potential bioterror attack, the city's health commissioner announced yesterday.

Dr. Peter L. Beilenson said that 1,750 hospital workers and 78 Health Department staff will be vaccinated, probably beginning soon after Jan. 24. That's when a provision in the federal Homeland Security Act takes effect that protects those who make or give the vaccine from lawsuits if those who receive it experience adverse reactions.

The vaccination effort will take between a month and 90 days, Beilenson said, and inoculations will be given at three sites across the city. Hospitals plan to stagger the inoculation of their workers, since many may get sick from the vaccine. In rare cases, the vaccine can lead to fatal complications.

Under the second phase of the city's smallpox plan, which will begin later next year, 10,000 to 20,000 additional health professionals will be vaccinated, Beilenson said.