Government scientists are fanning out to counsel some of the thousands of people weighing whether to get three shots of anthrax vaccine, more antibiotics — or to call it quits and hope their bodies are free of the bacteria.

In the wake of the anthrax attacks-by-mail, no one knows how many are really at risk of relapsing despite taking two months of antibiotics. Thus federal scientists offered the extra therapy as a precaution, yet can't say exactly who should take it. They are rejecting criticism that leaving it to individuals to decide is a cop-out. 

``Do we want to ... not make other options available to people but arbitrarily say 'No, we're not going to do anything else?' Or do we say we don't know everything?'' asked Dr. Jeffrey Koplan, director of the Centers for Disease Control and Prevention. 

CDC doctors injected 48 people, all Capitol Hill workers, with vaccine Thursday, set up hot lines and issued the first printed list of vaccine pros and cons to help others decide whether to try it. 

While anthrax vaccine itself is not experimental — it has been used for decades — it has never been used after exposure to the bacteria, so there's no guarantee it would help someone who relapses. It can cause side effects, so ``make sure that you know the risks and possible benefits before you agree to take part in this program,'' reads the CDC's consent document. 

The forms say: 

—Burning at the injection site is common, as are soreness, redness, itching and swelling of that arm for up to a week. Up to 35 percent of recipients have muscle and joint aches, malaise, rashes, chills, a low fever or nausea for up to a week. 

—Serious allergic reactions occur less than once in every 100,000 doses. 

—Studies of over 500,000 vaccinated people suggest reports of more severe reactions, such as muscle diseases, are not caused by the vaccine. 

—You cannot get anthrax from the vaccine. 

The shots also are controversial because they were made by BioPort Inc., which the Food and Drug Administration has not allowed to distribute its vaccine for several years because of manufacturing problems. But the FDA, which is working with BioPort to get routine production resumed, is allowing the CDC to use in the experimental vaccination program 10,000 doses that have passed manufacturer safety testing. 

One health department, in the nation's capital, advised against the vaccinations, disagreeing with CDC's conclusion that animal studies suggest relapse is a risk, albeit rare. 

At post offices in Washington and New Jersey, employees awaited arrival of CDC scientists promising one-on-one counseling about the extra therapy. Postal managers asked that the inoculations be delayed until Dec. 27, however, so employees in the holiday crunch have time to decide. 

``I still have questions about my own health,'' said postal vice president Azeezaly Jaffer, a candidate for vaccination who said CDC's consent form didn't give him enough information to decide. ``I still may choose, and that's just me, to talk to my own personal physician about what she thinks.'' 

Still, 48 Capitol Hill workers held out their arms for the first shots Thursday. 

One aide to Senate Majority Leader Tom Daschle said he took the shot because the military doctors advising him and his colleagues said they would've been vaccinated had they been exposed. Congressional workers agreed to discuss their decision only if their names weren't used, citing security concerns. 

For mail workers, the decision became more complex Thursday, when the CDC announced that its October testing of Washington's Brentwood central postal facility uncovered more widespread and intense contamination than previously revealed. Only two areas in the sprawling building were free of contamination after letters to Daschle, D-S.D., and fellow Democratic Sen. Patrick Leahy of Vermont passed through. 

Of the nation's 18 confirmed anthrax cases, four were among Brentwood workers. Two of them, plus a Floridian, a New Yorker and a Connecticut woman, died in the bioterror attack.
Vaccine recipients will get three shots at two-week intervals, and must take antibiotics until the vaccine kicks in with the third shot. Their health will be tracked for up to two years. 

People wanting more information may call the CDC at 1-888-246-2675, or, for Spanish speakers, 1-888-246-2857.