The alarms about side effects are louder, but the smallpox vaccine is no more dangerous today than it was 30 years ago.
The vaccine always has had significant risks. What has changed is that Americans are more informed and more litigious, prompting government and lawsuit-wary health providers to issue more emphatic and complete warnings, health experts said. More people also face medical problems — some serious, such as cancer, some not so serious, such as eczema — that make receiving the live-virus vaccine riskier.
"This is the most toxic vaccine given in the 20th century," said Dr. John Bartlett, chief of infectious diseases at Johns Hopkins University and co-founder of the university's Center for Civilian Biodefense Strategies.
Routine smallpox vaccinations, once legally required for schoolchildren, were halted in the United States in 1972. But in an attempt to prepare for a potential bioterrorist attack, the federal government will vaccinate 450,000 health care workers against the highly contagious and potentially fatal disease.
Pennsylvania will begin vaccinating about 22,500 health care workers as early as next week.
U.S. government and health officials recommend that the public get the vaccination only in the event of an attack, but President Bush has said it will be available to any adult who wants it.
Warnings of the vaccine's risks, ranging from flu-like symptoms to brain swelling to death, have been widely reported, and even some doctors and other health care workers say they will forego it because of potential problems.
Experts say it's the public that has changed since the days of routine inoculations, not the vaccine.
"It was given at a time when people accepted risks much more than they do now," Bartlett said. "In the 1960s, one in a million died; between 15 and 50 per million had some serious adverse reaction, and people accepted that. And now, if there's one adverse reaction in a million, people get crazy about it. We're just not the same society as we were."
Dr. Louis Tripoli, an expert in biological agents and an adjunct assistant professor of medicine at Johns Hopkins University, agreed.
"Back in the '50s or '60s, people just did what the doctor told them. There was not much concept of 'informed consent,'" he said.
His father, Dr. Charles Tripoli, a Washington County physician in practice since 1959, said doctors have become more rigorous in their warnings.
"We always gave it with some hesitation, but it was mandated by state law," Tripoli said.
Decades ago, he gave smallpox and other vaccines to children after verbally warning their parents of potential side effects, said Tripoli, 72. Today, vaccine warnings are much more extensive and in writing, which a parent must sign, he said.
The U.S. Centers for Disease Control and Prevention advise that people should not get the smallpox vaccine if they have certain health conditions, including immune-suppressing diseases, such as AIDS, HIV and rheumatoid arthritis, or eczema and other severe skin problems. Pregnant women and people taking steroids, undergoing chemotherapy or who are organ-transplant recipients also are advised not to get the vaccine.
The list also includes people living with or are having sex with someone with these conditions.
It's estimated about 30 percent of the U.S. population will not be eligible for the vaccine because of these restrictions, Bartlett said. Still, the risk of an adverse reaction even for people with some of these conditions, such as HIV and pregnancy, is low.
"I think people will be very cautious on this one, and I think part of the caution is because we don't have any experience on this in 30 years," Bartlett said.
For the same reasons, no one younger than 18 will be allowed to receive the vaccine unless there's an attack. In that case, officials recommend everyone, regardless of risk factors, get vaccinated.
In recent studies, about 30 percent of people who received the vaccine in tests at hospitals became sick enough to take off at least one day from their usual activities, which Johns Hopkins' Bartlett said is significant. Test subjects, like the health care workers soon to be vaccinated, were screened for possible problems, which should reduce the number of people who suffer adverse reactions, he said.
Adults who were vaccinated as children should have a lower risk of suffering an adverse reaction from the vaccine, unless they have developed a medical condition since then that puts them at risk, Bartlett said.
Those previously vaccinated also probably have some protection against smallpox, but how much is not known, according to the experts. Bartlett said they probably would be less likely to die or get a severe case.
The warnings from some health officials about the smallpox inoculations are motivated by legal factors, said Dr. Tom Stein, a bioterrorism expert and a medical director at Allegheny General Hospital.
"They're worried about people getting sued as much as they're worried about people getting sick," Stein said. "It's a million 'what ifs.' We keep forgetting we did this for decades and decades."
