Florida would need to set up more than 300 temporary sites to vaccinate the state's 16.4 million residents within 10 days of a massive terrorist smallpox attack, state health officials say.

On Monday, the Centers for Disease Control and Prevention announced a nationwide plan under which it would provide 280 million doses of the vaccine within a week of such an attack.

''It's very realistic,'' said Dr. John O. Agwunobi, secretary of the Florida Department of Health. ``Given the political realities that exist, I think we need to be prepared for a mass vaccination.''

Florida's plan would use state and local health department personnel and possibly even National Guard troops to administer the vaccines in clinics, schools and hospitals.

But some health experts criticized the plan as too big to be easily implemented.

''The plan is well done, but I'm concerned that it relies on the states to do the work,'' said Dr. Mohammed Akhter, executive director of the American Public Health Association. ``States don't have the resources for the massive job of vaccinating every man, woman and child.''

Agwunobi said Florida is well positioned to help implement such a plan.

``We already have the foundations of a program to vaccinate our population, set up as part of our pandemic influenza plan. We're prepared not for one specific infection, but for any one.''

Florida's plan will be coordinated by the state's already existing disaster planning apparatus -- the seven Regional Domestic Security Task Forces and their health subcommittees, Agwunobi said.

In South Florida, the health subcommittee is co-chaired by Dr. James J. James, director of the Miami-Dade County Health Department and Wil Trower, CEO of the North Broward Hospital District.

Each region will identify key vaccination sites and the resources to staff them.

In Broward, for example, vaccination sites could be set up in the same public schools that are used as hurricane shelters, says County Health Department spokeswoman Ellen Feiler. National Guard troops could supplement county health personnel, she said.

The Miami-Dade Health Department is awaiting state orders before implementing its plan, a spokeswoman said.

On the national level, it remained unclear as to who would order such a mass vaccination and under what conditions.

''The decision around mass vaccination would be dependent on the particulars of the outbreak we were facing,'' said Dr. David Fleming, deputy director for science of the Centers for Disease Control and Prevention. ``We've got to develop the plans right now.''

But since smallpox was declared eradicated from the Earth in 1980, even one new case might trigger alarm and a major response. Routine immunizations in the United States ended in 1971, leaving most of the U.S. population with little immunity.

Smallpox is particularly feared by experts because it's highly contagious -- it can be spread by a cough -- and in its most lethal form, it can kill one out of three people who contract it. But a massive attack is considered unlikely as the virus is believed to exist only in government labs in Washington and Moscow.

Still, a single new case ''would suggest the likelihood of other cases of the highly contagious disease popping up and therefore suggest the need for a fairly widespread control program,'' said Dr. Walter Orenstein, director of the CDC's National Immunization Program.

''Once there is a case of smallpox, what has been theoretical up until now suddenly becomes real,'' said Dr. Julie Gerberding, director of the Centers for Disease Control and Prevention. ``We would anticipate many Americans would want to have access to the vaccine.''

Deciding who gets the vaccine first is a contentious issue.

Akhter, of the American Public Health Association, proposes vaccinating America's 11 million or so ''first responders'' -- medics, emergency personnel, firefighters -- now. And he would start other vaccinations if a terrorist threat is imminent, not waiting for an actual smallpox attack.

The CDC has not decided yet what position to take on this subject but says it will decide soon.

The 48-page CDC vaccination plan released Monday offers specific suggestions for implementation by state and local health departments, including:

• Medical consent forms and information for distribution about smallpox and the side effects of the vaccine.

• Details about how to store and prepare the vaccine.

• A list of places where security or crowd control will be needed, including clinics and vaccine storage sites.

• Types and numbers of workers needed per clinic, including volunteers to run an informational video, nurses to give the shots and translators to assist non-English speakers.

• Criteria for choosing a vaccine clinic site before a smallpox attack.

• Guidance about who should not receive the vaccine due to heightened risk of side effects.

This report was supplemented by Herald wire services.