WASHINGTON -- Top federal health officials said Friday they favor offering the smallpox vaccine in stages: first to all who work in hospital emergency rooms, then to about 10 million health care and emergency workers, and eventually to the general public.

In their first public statements about who they believe should be vaccinated in advance of an attack, health officials emphasized that no decision have been made. That decision rests with the White House, where some have been pushing for an even more aggressive program, vaccinating more people more quickly, according to health and White House officials.

The smallpox decision is a difficult one. An attack with the highly contagious virus could be devastating, as it kills one-third of its victims. But the vaccine itself also carries rare but serious risks, including death, and no one knows whether an attack will ever come.

Health officials offered no timetables for vaccinations but said they favor waiting until the vaccine is licensed, rather than delivering it as an experimental drug. The first batch of shots will be licensed in November, but it will be over a year before enough licensed vaccine is available for mass inoculation.

This approach is more cautious than pushing ahead quickly with unlicensed shots, but far more aggressive than recommendations of just a few months ago. At that time, an advisory committee said the shots should only go to a handful of people working in state smallpox response teams and at select hospitals -- maybe 20,000 people total.

Context 'changed a bit'

Since then, the United States has pushed toward war with Iraq, which experts fear has smallpox in hand and could release it in an act of bioterror, said Dr. Julie Gerberding, director of the Centers for Disease Control and Prevention.

"We need to be mindful that the context of this decision has changed a bit," she said Friday.

Smallpox hasn't been seen in this country for half a century, and routine vaccinations ended in 1971. In 1980, the disease was declared eradicated from the globe. Officials aren't sure how much protection remains for adults who were vaccinated as children.

Gerberding said that the plan that health officials now favor would offer the vaccinations in stages, beginning with those at greatest risk and then moving to others, creating "ongoing and ever-expanding access to immunization."

Top officials had detailed this plan on condition of anonymity to The Associated Press last month, but Friday's comments at a briefing for reporters represented the first public confirmation of their thinking.

Under the plan favored by Gerberding and other top health officials, the vaccine would first be offered to people working in emergency rooms -- everyone from doctors and nurses to janitors and security guards -- because they are at the greatest risk of encountering a highly contagious smallpox patient. Also in the first round: state teams that would investigate any suspicious patients.

An estimated 500,000 people are expected to take the vaccine during this first phase, said Jerry Hauer, the top bioterrorism official at the Department of Health and Human Services. He said that estimate was derived by assuming that half of the nation's 5,000 hospitals would choose to offer the shots, with an average of 200 people at each.

In the next phase, the vaccine would be offered to about 10 million others, including all other health care workers, who total 7 million to 7.5 million, plus police, fire and other emergency workers, who total about 3 million, Hauer said.

At some point after that, the vaccination would be offered to the general public.

"Right now, our thinking is in favor of making vaccine available to the general public," Gerberding said, adding: "We live in a society that values individual choice."

Dr. Anthony Fauci, director of the National Institute for Allergy and Infectious Diseases, said it's possible that Bush will opt to speed up the timetable, an option Vice President Dick Cheney and others are pushing. For instance, he said, Bush might want to vaccinate all 10 million health and emergency workers right away, or he might want to offer it to the general public before it is licensed. Health officials would support those permutations of their thinking, he said.

Just a year ago, the nation only had 15.4 million doses of vaccine in hand, but there now is enough for every American, thanks to fast-track purchasing, studies that found the existing vaccine can be watered down and a drug company that discovered 86 million doses in its freezer.

But none of this has been licensed by the Food and Drug Administration yet.