WASHINGTON?Some 32,000 people have been prescribed antibiotics in the anthrax crisis, 5,000 of whom really needed them and thus must take the pills a full 60 days, health officials said Thursday.

Medical authorities said in new guidelines that merely finding traces of anthrax clinging to surfaces does not warrant closing buildings or prescribing antibiotics.

President Bush, on a visit to the Centers for Disease Control and Prevention in Atlanta, expressed reservations about vaccinating all Americans against smallpox. The disease has been eradicated, but could return in an act of bioterrorism. He noted the vaccine occasionally has fatal side effects.

“I would be deeply concerned about a vaccination program that would cause people to lose their lives,” said Bush, who has asked Congress for a $500 million to stockpile the vaccine.