In a series of interviews and published articles, Pentagon officials, conservative thinkers and a few public health officials argue that without a sizable network of inoculated health care workers, the United States remains ill-equipped to respond to a smallpox attack. And, they contend, anxiety about the dangerous side effects of the vaccine should be quelled by the success of the military in immunizing nearly a half-million personnel with few serious complications.

"Our goal at this point should be to meet [President Bush's] plan and to vaccinate the number of people originally targeted in the health care community of between 400,000 and 500,000," said William Winkenwerder Jr., assistant secretary of defense for health affairs. "I would certainly be more comfortable if we had that number of civilians prepared to respond."

At the Centers for Disease Control and Prevention in Atlanta, Director Julie L. Gerberding said she hopes to unveil a strategy soon to "reaffirm the importance of the smallpox program because of the dreaded consequences" of an attack. The agency plans to distribute $100 million to states to step up vaccinations.

But even some supporters of the Bush policy say the opportunity to vaccinate millions before an attack has been missed, with the effort plagued by mixed messages, safety fears and the lack of evidence that Saddam Hussein possessed stocks of the deadly virus.

"People are now back in dumb-and-happy mode," said Tara O'Toole, director of the Center for Civilian Biodefense Strategies at Johns Hopkins University. Gone, she said, is the sense of urgency that people felt last winter "when we were going into Iraq, and the possibility of a smallpox attack was seen as much more plausible."

Seven months after the president announced he was resuming smallpox inoculations, after a 30-year hiatus, as part of the effort to protect the United States against biological attacks, the program is in danger of virtually vanishing.

In recent months, top officials such as Bush, Vice President Cheney and Homeland Security Secretary Tom Ridge have rarely mentioned the threat of a smallpox attack or the need to vaccinate millions of emergency responders. Neither has Senate Majority Leader Bill Frist (R-Tenn.) or Surgeon General Richard H. Carmona, although both were immunized in front of cameras to publicize the effort in March.

With few exceptions, state and local health departments have shifted their attention to more immediate concerns, such as severe acute respiratory syndrome (SARS), West Nile virus and back-to-school shots. And two respected groups -- the Institute of Medicine and the CDC's Advisory Committee on Immunization Practices -- have called for a halt to smallpox vaccinations, citing concerns about heart complications related to the vaccine.

To date, fewer than 40,000 public health and hospital employees have been immunized. And despite Bush's promise to make vaccine shots available to the general public this summer, Gerberding said yesterday that a new vaccine will not be ready for another year. Nearly 50,000 doses of smallpox vaccine have been discarded because the opened vials had passed their expiration dates.

All of that frightens William Bicknell and Kenneth Bloem, two smallpox experts who drafted a position paper for the libertarian Cato Institute warning that the United States has not done enough to prepare.

"We should be well on our way to protecting the nation's civilian population by vaccinating up to 10 million health, emergency and public safety workers. However, we are stalled," the pair wrote. "We call on CDC to do a far better job in publicizing the safety of vaccination for healthy adults and we call on the Bush administration to revitalize our preparations for a smallpox bioterrorist event."

The sharpest criticism of the vaccination campaign has been that Bush and his deputies failed to articulate -- and continually reinforce -- a rationale for using a vaccine known for its side effects. Though she is well-versed and plugged-in, even O'Toole said: "To this day, I don't know what the purpose was."

Some now fret that Bush's declaration that hostilities in Iraq have ended left the mistaken impression there is no longer a threat.

"We know that the former Soviet Union had large quantities of weaponized smallpox or smallpox that could be used in an offensive manner," Winkenwerder said. "All of those stores are not accounted for, to our knowledge."

He and Army Col. John D. Grabenstein, a physician overseeing Pentagon vaccinations, published an article in the Journal of the American Medical Association detailing the results of the military program in an attempt to encourage participation in the civilian program.

"It is our hope and desire that in relating our experience to the broad general public the point can be made that what we accomplished can be accomplished by others in the civilian sector," he said. "There is nothing unique in what we did."

The CDC calculated last year that it would take 1.25 million immunized health workers to run enough emergency clinics to immunize the U.S. population within 10 days in the event of an attack. Yale University professor Edward Kaplan said he has seen no evidence the country is near that capability.

"If you believe it's a serious threat -- and plenty of credible folks do believe it is a threat -- then it makes sense to be ready to push the button" on mass immunization, Kaplan said. "We are not in a position to respond rapidly if we have to."

Michael T. Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy, said that he would prefer to have the 1.25 million health workers immunized in advance but that it would "not be a major crisis" if officials spent the first day of an outbreak doing that.

Gerberding said she feels frustrated by the emphasis on the small number of people immunized so far. She said the CDC has not been given credit for its accomplishments, including purchasing 150 million doses of vaccine, educating and training the medical community, upgrading state laboratories, expanding hospital capabilities and overseeing emergency drills.

"Can we stand up clinics across the country tomorrow to immunize our nation in 10 days? No," she acknowledged. Still, we "have made enormous progress."

Ultimately, Gerberding said, it is up to the states to decide how they will prepare for terrorism, including a possible smallpox attack.

That helps explain the wide variation in inoculation rates across the country. Some states, such as Arizona and Nevada, have immunized fewer than 50 people, while Tennessee has immunized 2,500.

Washington state initially estimated that it would vaccinate 7,000 medical personnel, said Health Secretary Mary C. Selecky, who is president of the Association of State and Territorial Health Officials. But concerns over liability and reports of heart complications in some vaccine recipients dampened enthusiasm, and just 543 have been immunized. She said she has shifted her strategy to identifying people who are ready and willing to be immunized at the first report of a smallpox case.

Florida Health Secretary John O. Agwunobi pushed hard to recruit a corps of 3,900 immunized medical workers spread evenly across all 67 counties -- and he hopes to continue.

"We are working on the premise the threat remains," he said. "We're open for business."