In his old files, Richard P. Wenzel keeps a photograph of a patient's chest dotted with smallpox pustules.

Taken in 1967 in what is now Bangladesh, where Wenzel served part of his medical residency, the grainy picture used to seem more a historical curiosity than an ominous portent.

Now chairman of internal medicine at Virginia Commonwealth University's teaching hospital, Wenzel is among the few physicians who have firsthand knowledge of a disease not seen in the United States since 1949 or in the world since 1977. Yet when the government asked the nation's hospitals to inoculate health care workers in advance of a possible smallpox terror attack, Wenzel helped persuade the VCU Health System not to participate just yet.

"We focused on a purely medical risk-benefit analysis," he said. "Suppose 100 people get inoculated, and one gets encephalitis. I'd have to look that family in the face and tell them there's been no smallpox for 20 or 30 years."

At Virginia's other teaching hospital at the University of Virginia in Charlottesville, Frederick G. Hayden, chairman of the hospital's infection control committee, drew a different conclusion. "The risk is extremely low. Not zero, but low," he said of the vaccine, which may be fatal to one or two people in a million. "What swayed my thinking was our proximity to D.C. If there is a large-scale introduction of the virus into the general population, we're likely to take care of individuals here in Charlottesville."

Virginia's two teaching hospitals illustrate the ongoing debate within the medical community over the wisdom and necessity of inoculating front-line health care workers who would treat victims should terrorists use stolen smallpox virus as a weapon.

The Bush administration aims to immunize 500,000 medical workers initially, and eventually as many as 10.5 million. But with the risks known and the threat uncertain, the program has stumbled over concern about side effects and compensation for workers who become ill. Barely 1,000 workers have been vaccinated so far, more than 100 hospitals have opted out of the program and hundreds more remain undecided.

The first immunizations in the Washington area will begin his week. Public health workers from Montgomery, Prince George's and Howard counties will be vaccinated at a secret site guarded by police. Vaccinations will be offered tomorrow to Prince William County public health workers, who in turn will inoculate hospital employees Friday. Fairfax County has not even designated public health nurses to be vaccinated. Immunizations in the District begin March 3.

In preparation, hospitals across the region are holding town meetings and small seminars for employees to explain the vaccine and sick-leave policies. Every hospital in Maryland and the District has agreed to participate, health officials say. Hospitals in Northern Virginia are all drawing up cadres of workers, but elsewhere in the state many hospitals have delayed a decision.

"Some are gung-ho and have more volunteers than they dreamed of," said Carl W. Armstrong, vice president of the Virginia Hospital and Healthcare Association. "Others have very few. And still others are wrestling with the decision. They're all trying to do what's best for their community. But what we're hearing is that as people learn the issues and concerns, there are fewer who say they want it."

In the District, the nonprofit Whitman-Walker Clinic has discouraged its staff members from getting the vaccine because of the potential risk of exposing people with HIV. The American Nurses Association calls it a personal decision but advises its members to be fully informed of the potential health risks and to make sure their insurance covers illness due to the vaccine.

A small percentage of people are expected to suffer complications, some as extreme as blindness and encephalitis, swelling of the brain. Of the 100,000 or so members of the U.S. military who have been inoculated, three suffered side effects, including two with encephalitis.

The vaccine, which cannot itself cause smallpox, is not recommended for tens of millions of Americans, among them people who are HIV-positive, recipients of organ transplants, pregnant or under treatment for cancer or eczema.

"It's a risky vaccine, but the risk of smallpox is far greater," said Jeffrey A. Elting, medical director of hospital bioterrorism preparedness for the D.C. Hospital Association, noting that one out of three who used to get the disease died. "It probably is common sense to get the vaccine if you're in one of the top terrorist targets in the world."

So far, the threat implicit with living in the nation's capital is reason enough for many health care workers to volunteer.

"It's hubris for us to say the risk is not great enough to want to put our employees at risk," said Daniel Ein, chairman of the emergency preparedness committee of the Medical Society of D.C. "The ethical thing for the medical community to do is to be available and help our patients. Putting ourselves at risk to help the sick is part of our tradition. I think it's wrong, socially, politically and ethically, to make the decision that VCU made. The risk is very small. One out of 1 million is going to die. That's less of a risk than driving a car."

At VCU, hospital epidemiologist Michael Edmond approached the vaccination program with an open mind. Smallpox was already eradicated and not even taught when he attended medical school in the 1980s. But when Edmond looked at the list of conditions for which the vaccine is inadvisable, what he saw was a fair synopsis of the hospital's patient population.

"The more I read about it, the more I thought it was something we should not do," he said. "It's a safety issue for patients. The risks appear to outweigh the benefits. I kept thinking of that old aphorism: First do no harm."

Edmond also questioned whether he could "sell" the vaccine to staff members once they learned all the risks.

"The vaccine poses significant risks for them, their families and their patients," he said. "All for a disease that doesn't exist."

The risks associated with the vaccine are less acceptable today than they were in 1966, when Edmond's mother took him for a smallpox shot with little ado.

"She also let me ride a bike without a helmet and get in a car without seat belts," he said. "We have all moved beyond those days. It's the perception of society and the risks we are willing to take."

A window of four days exists for effective vaccination after the initial exposure. Under the policy approved by the hospital's infectious control, executive and ethics committees, a post-exposure plan sets the goal of vaccinating the entire workforce within 24 hours.

"Why do we have to rush to vaccinate now when we can vaccinate post-exposure?" Wenzel said. "If there's one case anywhere in the world, I don't care if it's in Madagascar, that's enough to say it's possible and we should respond and protect ourselves."

In contrast, administrators and physicians at the University of Virginia Health System wanted to be part of the immunization program from the start. They have the same information as the doctors at VCU. But their focus is different.

"Smallpox is a disease we can do something about," said William A. Petri Jr., the head of infectious diseases and internal health at the hospital, which is actively seeking 135 employees, ranging from physicians and nurses to admissions clerks, to be immunized. "We can't do anything about anthrax. It's better to be prepared."

The hospital's experience with flu vaccinations influenced the decision to immunize a front-line team for smallpox. Since actively promoting flu shots for employees and posting signs advising visitors with flu symptoms to stay away, worker absenteeism and patient cases of flu have declined dramatically.

"There are some analogies to smallpox," said Hayden, also a professor of medicine. "If there is a real smallpox event with a lot of individuals exposed, to have immunized workers will diminish the risk of disease and death."

Hayden, who has been vaccinated, calculates that the likelihood of terrorists reintroducing smallpox to the world is far greater than the health risk to patients and employees.

"We don't have concrete numbers on the benefit if, God forbid, we ever need it," he said. "But the numbers are reassuring. The likelihood of risk to patients is extremely remote."

Petri gave a similar message when he met with four nurses to explain the vaccine and its potential side effects.

"Why the hype?" asked one nurse, who remembered being immunized as a child.

"It's not totally safe," Petri replied, enumerating the expectation that a few people will get encephalitis and occasionally someone will die. "That was probably acceptable 40 or 50 years ago when we were eradicating the disease."

But health care workers accept a certain level a risk that they may acquire a disease when they enter the profession, he said.

"The risks of the vaccine are known," he said. "Where we disagree with VCU is what the risk is that smallpox can be used as a weapon. I have to rely on people in the U.S. government who came to the judgment to make the vaccine available and put in this program."

Daniel Sawyer, a physician at Martha Jefferson Hospital in Charlottesville, receives a smallpox inoculation from nurse Debbie Childs.