The AMA's governing House of Delegates, meeting in San Francisco, instead asked the U.S. government to evaluate the risks and benefits of mass vaccination while continuing to plan for a program should the need arise.
"The science would not indicate that mass vaccination is the appropriate thing to do," Dr. John Nelson, a member of the AMA's board of trustees, told a news conference.
The U.S. government last month ordered additional smallpox vaccine doses to build a stockpile large enough to vaccinate every American against the disease, but officials said they were not planning to launch a mass immunization program.
Acambis Plc and Baxter International Inc. jointly will produce the new shots for $428 million, with delivery expected by next fall.
U.S. health officials accelerated efforts to prepare for a smallpox attack after the Sept. 11 attacks that killed about 3,900 people and as five people died in a mysterious rash of anthrax attacks starting in early October.
Smallpox was eradicated more than two decades ago, but experts fear it could resurface if there were a biological attack. Easily spread from person to person, it kills about 30 percent of its victims and leaves others disfigured. There is no effective treatment once someone falls ill, but giving a vaccine in the days immediately following exposure can prevent illness.
The AMA, the nation's largest and most influential doctors' group, noted that the Centers for Disease Control and Prevention was against a mass inoculation program in part out of fears that some people - roughly one in every million - could die from adverse reaction to the smallpox vaccine.
"If you vaccinate the whole country, you could have as many as 300 Americans who would die as a result of that mass vaccination itself," said Dr. Ron Davis, a public health expert and AMA board member.
Davis said the AMA instead supports the study of alternative vaccination strategies, such as immunizing "rings" of people around smallpox cases once any have been detected.
"This is the strategy that worked in eradicating smallpox from the world back in the 1960's and 1970's," he said.
The AMA's action Tuesday was in response to a proposal by Florida doctors that the AMA back nationwide vaccines despite those risks.
"We are at threat," Dr. Bernd Wollschlaeger of North Miami Beach, Fla., said during debate of the issue on Sunday.
Others urged the AMA to endorse voluntary vaccinations that would be left to the discretion of prescribing doctors.
But Davis pointed out Tuesday that the United States has only 15.4 million doses of vaccine currently available. The federal government did recently agree to pay a total of $428 million to Baxter International Inc. and Acambi Plc. for 155 million doses of smallpox vaccine. But those new doses won't be available for at least a year.
Until then, Dr. Joy Maxey of Atlanta advocated inoculating doctors such as herself to protect against contracting the disease from patients.
"We should at least be offered that opportunity," Maxey said Tuesday. The AMA sent Maxey's proposal to vaccine so-called "front-line defenders" such as doctors and paramedics to a committee for study.
AMA officials said the nation's medical community was still carefully evaluating the potential risk posed by smallpox and other bioterror agents, and was working hard to educate doctors about diseases that many have never seen in their professional careers.
But they stressed that the current information did not warrant a crash smallpox vaccination program.
"Let's make sure that science rules the day," Nelson said. "We need to make sure that we maintain as much calm as possible."
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