Smallpox vaccine in flux for doctors. (CDC, HHS Consider Recommendations).

ATLANTA -- The risk of exposure to smallpox is too small--and the risk posed by the vaccine too great--to justify vaccinating most physicians at this time, the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices recommended at its annual summer meeting.

In the absence of an act of smallpox bioterrorism, ACIP advised against vaccinating physicians other than those on designated "smallpox response teams" and selected health care personnel in facilities to be designated as smallpox referral centers.

CDC officials estimated at the meeting that perhaps 15,000-20,000 people would be vaccinated under this plan. The ACIP recommendations included no numbers, however, and news reports have since said that this population could include as many as 500,000 people.

"The 500,000 [figure] could be right, it could be high, or it could be low," Health and Human Services spokesman Bill Pierce said in an interview. The CDC and the HHS are reviewing ACIP's recommendations in the coming weeks before issuing a policy.

The debate also may shift as a result of a Yale University report published online July 15 in the Proceedings of the National Academy of Sciences (www.pnas.org). This epidemiologic modeling study suggests that the "ring" vaccination approach would likely result in far more cases and deaths than if mass vaccination were applied in the event of a smallpox bioterrorist attack in a large U.S. city.

Ring vaccination was used to eradicate wild cases of smallpox. In ring vaccination, the case's household members and other dose contacts and their contacts are vaccinated.

In its recommendations, ACIP advised that, in the absence of an outbreak, smallpox response teams, trained to investigate suspected smallpox cases and establish control measures, would be vaccinated. Teams might include medical epidemiologists, laboratory scientists, and security/law enforcement personnel. Each state would establish one or more such teams--no numbers have been decided as yet.