BBC News Online: World: Americas

US offers anthrax vaccine

Senate employees wait to report for work

Congressional staff and postal workers are thought to be at greatest risk, and are being offered the treatment in case any anthrax still lurks in their lungs.

Correspondents say the offer of vaccination is intended to reassure, but may have the opposite effect.

Up to now the official position had been that anthrax could only incubate for a maximum of 60 days.

But the authorities now say it is conceivable the spores could still linger in the body after two months.

Side effect concerns

However, the vaccination will be experimental as no one is certain of its effect after possible exposure to the disease, and there are concerns about side effects.

Some postal workers are saying they have had a bad enough time taking the 60-day course of antibiotics, and will not even consider the vaccine.

"Some of these people, especially those who may have been exposed to high levels of anthrax spores may wish to take additional precautions beyond completing the 60-day antibiotic regimens," US Health and Human Services Secretary Tommy Thompson said.

US authorities revealed on Monday that the anthrax bacteria used in the recent string of attacks did not come from the country's military stocks.

The denial came after the Washington Post quoted scientists investigating anthrax mailed to Capitol Hill as saying that tests had found it identical to a strain developed by US Army scientists at Fort Detrick in Maryland.