The Centers for Disease Control and Prevention said it may give the anthrax vaccine to its high-risk workers, including those decontaminating infected sites in four states.

The program would cover about 800 lab workers who are part of the Laboratory Response Network, a nationwide organization of about 100 public and private facilities involved in testing anthrax samples as part of the federal investigation, CDC spokeswoman Kathy Harben said Friday.

"CDC workers conduct the testing as well, and lab workers at CDC involved in testing would also be recommended to receive it," she said.

Dr. David Flemming, the CDC's director of science and public health, said the vaccine recommendation may expand to include postal workers and others at risk of repeated exposures to anthrax.

Harben said the agency is working with the Defense Department, which controls the nation's limited stores of anthrax vaccine, and with various state agencies to provide the vaccine.

The vaccination requires six doses administered over 18 months.