Public health experts next month will begin drafting a policy designed to protect every person in the United States against smallpox. The issue is unprecedented: It's the first time the country will attempt to develop a vaccine policy against a disease that has been eradicated.

Driving the efforts are the anthrax attacks of the fall, which generated an awareness that bioterrorism can be a potent agent in the country's health. The insidious anthrax-by-mail campaign resulted in 18 infections and five deaths.

By year's end the federal government will have stockpiled enough smallpox vaccine to immunize every man, woman and child in the United States. Under debate will be just who should receive it.

Policymakers are aware of a wide range of views, but are likely to recommend immunizing only health care workers and other emergency responders prior to an attack. Already, top health experts are publicly lining up against mass vaccinations, primarily due to the known side effects.

"This is not a benign vaccine," said Dr. Sharon Frey, a smallpox vaccine expert at St. Louis University in Missouri. Risks include death in one out of every 1 million people who receive it; brain damage in a small fraction of children, and body-covering sores in people who have eczema.

But without a policy, say experts on bioterrorism, Americans could find themselves at the mercy of a diabolical plot.

On May 8-9, a sub-panel of the federal Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices will gather near Atlanta to get the debate under way. The public will have an opportunity to comment in forums to be announced next month.

Among approaches being discussed are:

A mass vaccination campaign, in which everyone in the country is vaccinated. This approach is not expected to be popular among vaccine experts at the meeting.

Vaccinating ambulance attendants, health care workers, firefighters, police officers and other "first responders" to an emergency. This would be a way to implement the "ring scenario," focusing on vaccinating infected people and all of their contacts.

Vaccinating just those who want it.

Distributing smallpox vaccine doses to states, allowing public health officials in each state to decide on preparedness plans.

Vaccinating the entire U.S. population for smallpox in the 21st century, without signs of an attack, is a step some vaccine experts call extreme. Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said he would not even entertain it, saying "that's exactly the question I do not want to address."

Dr. John Modlin, who will co-chair the meeting, said, "We need a policy, but that doesn't mean that we have a general policy to immunize large numbers of people."

Modlin, a professor at Dartmouth's medical school in Hanover, N.H., added that because the vaccine is based on a live virus, a policy must be carefully crafted. For instance, he said, people with weak immune systems - people with AIDS, those undergoing chemotherapy and those on immunosuppressive drugs for organ transplants - could never receive it because they would be sickened by the inoculation.

"What we want to do is discuss the background regarding the disease and try to assess what smallpox would be like in a bioterrorist event," Modlin said. "And in such a case, determine the best way to respond so that we can reduce morbidity and mortality. We want to lay out the issues and generate the appropriate questions."

Though experts on bioterrorism say they believe the possibility of a smallpox attack is remote, they also believe that the virus was probably replicated from existing stocks years ago and is in the hands of potential terrorists.

Only two sets of viral specimens existed after a global vaccination campaign resulted in worldwide eradication in the 1970s. One set was kept by the United States at the CDC in Atlanta. The other samples were retained by the Soviet Union. One theorist, Dr. D.A. Henderson, director of Public Health Preparedness in the U.S. Department of Health and Human Services and an adviser to the federal Homeland Security operation, says he believes disgruntled Soviet scientists gave samples to the Iranians and North Koreans after communism's fall.

"The Russian biological weapons program was the same size as their nuclear weapons program with 60,000 workers," Henderson said in an interview last fall. Being prepared for smallpox is vital to national defense, he and other experts say.

"A smallpox attack could come tomorrow, it could come next week, or 20 years from now," said Frey. "It may never come. There are so many unknowns."

She was lead investigator of a study released in late March showing that the nation's available doses of smallpox vaccine could be diluted, and therefore stretched to cover more people. That discovery, coupled with the donation of 83 million doses that had sat untouched for 44 years in a pharmaceutical company's freezers in Pennsylvania, instantly boosted the stockpile. New batches purchased by the federal government from a British vaccine maker will arrive later this year.

The notion that smallpox could be used as a terrorist weapon became a topic of high-level discussions during the height of the anthrax scare. Separate discussions are under way at the CDC on a health policy for anthrax.

An ancient scourge, smallpox is highly contagious and fever-inducing. It is typified by weepy, crusting sores and carries a 30 percent death rate. Its use as a weapon dates back centuries.

The public will be brought into the talks in June. By late June or July, the CDC's full Advisory Committee on Immunization Practices is expected to finalize a strategy, CDC spokesman Curtis Allen said.

Clamor is growing for immunizing anyone who wants the smallpox vaccine. "We live in a free country and if the government has the vaccine it should not sit on it. I am not calling for mass vaccinations, just vaccinations for those who want it," said Charles Peña, a senior defense policy analyst for the Cato Institute, a nonprofit public policy think tank in Washington, D.C.

Peña and a fellow Cato analyst have completed a study on bioterror and smallpox, concluding that immunizing people who want the vaccine would help prevent mass panic in the event of an attack.

Gary Cox, director of the City-County Health Department in Tulsa, Okla., is in favor of states having supplies of the vaccine. He also told a U.S. Senate Committee hearing on homeland security earlier this month that federal money is needed to upgrade state disease surveillance and response systems. This year the federal government is spending $940 million to improve such infrastructures.

In an interview, Cox said state governments probably would be better equipped to vaccinate people quickly in the event of an attack. Currently, the vaccine is part of the National Pharmaceutical Stockpile, which is in secret regional locations.

"I think it's wise to rely on the CDC's expertise and consult with them," Cox said, "but I also think giving more control to state and local governments is a good thing."

Dr. Georges Peter, professor of pediatrics at Brown University who will co-chair the May meeting, said he supports the "ring vaccination" plan. "People have forgotten how serious a disease smallpox can be," Peter said, so getting a policy in place is vital.

In a ring scenario, immunized emergency workers would respond to people stricken with smallpox virus. Infected people and all of their contacts - infected or not - would be vaccinated. Within the first few days of exposure, the vaccine can trigger an immune response powerful enough to combat infection.

That scenario, Peter said, mimics the strategy used during the global smallpox vaccination campaign of the 1960s and '70s.

But Frey, who is not part of the policymaking meetings, said that in a bioterrorist attack, the ring strategy could have serious drawbacks.

"Technically, it sounds good," she said, "but it's based on regions of the world where many of the people were already immunized." The presence of immunized people throughout communities limited the spread of the disease.

"With bioterrorism, it's not like a bomb going off," said Peña. "The terrorists are not going to announce this. The only way people are going to know about an attack is when people start going to their doctors with symptoms, and the initial symptoms of smallpox are a lot like the flu.

"So if an attack happens in flu season, do you really think a doctor will diagnose smallpox? That's a problem I have with the ring vaccination plan."

The last case of smallpox in this country was 1949, and vaccination stopped in 1972. Millions of people under age 30 have never been immunized, and for millions more over 30, the vaccine's effects probably have worn off, doctors say. Coming up with a policy now, Frey said, would help the nation avoid pitfalls similar to the great swine flu debacle of 1976.

President Gerald Ford, following the advice of medical advisers, ordered vaccination of the entire population, but the predicted sweep of a killer flu never occurred. The vaccination program was stopped midway, and top government health officials were fired under accusations of a botched campaign. Foremost among the problems, said critics, was predicting an epidemic with so little evidence that one was on the way.

A flurry of lawsuits followed from people claiming they were sickened by the vaccine. Given the potential side effects from a live-virus smallpox vaccine, a little caution could go a long way, Frey said.

Disease's Deadly Past

Smallpox, a fatal and highly contagious disease spread through inhalation, was once widespread throughout the world. In the 20th century alone, the disease killed about 300 million before it was eradicated worldwide.

1157 B.C.: Ramses V of Egypt died in the first suspected case of smallpox. Thousands of years later, scientists found smallpox traces on the pharaoh's mummified face.

710: Smallpox reached Europe.

1518: Carried by the Spaniards, the

1519-1521:Smallpox wiped out about 3.5 million Aztecs, leading to their defeat by Hernando Cortes' Spaniards.

1700s: In Europe, smallpox, now an epidemic, decimated large parts of the population.

1763: Hoping to stop local tribes' attacks on settlers, British soldiers gave American Indians blankets infected with smallpox, marking the first time the virus was used as a weapon of war.

1796: English medical student Edward Jenner made a breakthrough when he found that people infected with the milder cowpox - a disease that afflicts mostly cows - were immune to smallpox. He dubbed the inoculation "vaccinia.''

1949: Last case of smallpox in U.S.

1967: The World Health Organization began a global vaccination program.

1972: Facing a mild outbreak, Yugoslavia sealed its borders and ordered a vaccination of 20 million people. In the United States all vaccination was stopped.

1978: World's last recorded smallpox death.

1979: The WHO declared smallpox eradicated.

Fall 2001: In the United States, anthrax attacks, whose victims included Kathy Nguyen, increase fears of a biological attack and spur new efforts to develop a smallpox vaccination policy.