US health officials are considering giving the anthrax vaccine to 3000 people who were exposed in the recent postal attacks. The decision comes amid concern that inhaled spores may linger in people’s lungs and then germinate after the end of the antibiotics course prescribed for those affected.
About 10,000 people have been taking antibiotics, mainly ciprofloxacin, after they were potentially exposed to anthrax in letters posted in early October. Most of them work in US Postal Service sorting offices where two anthrax-laced letters were processed by high-speed equipment, forcing spores out of the envelopes. Two postal workers died of inhalational anthrax as a result, and more became ill.
Of those 10,000, the Centers for Disease Control and Prevention in Atlanta says 3000 are at greater risk, either because they worked in the Senate offices where the letters were opened, or because they worked where other postal employees fell ill.
Some have finished their 60-day course of preventive antibiotics, but are being advised to continue to take the pills as officials decide about vaccination. However, up to three-quarters of postal workers are reported to have already stopped taking their antibiotics because of side effects including nausea, dizziness and diarrhoea.
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Tough and inert
Anthrax is inhaled as a tough, inert spore that then germinates into the growing bacteria that cause disease. Antibiotics kill only this growing form. But not all spores germinate at once and, in animal experiments, as many as one per cent of them had not germinated as long as 75 days after inhalation.
Using both antibiotics and vaccination means that when the antibiotics are over, the vaccine has induced enough immunity to deal with any spores that germinate subsequently.
The CDC acquired 220,000 doses of anthrax vaccine from its sole manufacturer, BioPort of Michigan, last week, along with temporary permission from the US Food and Drug Administration to use it.
But it is questionable how many people will take the jabs even if they are offered. The 1950s-vintage vaccine, made from a variable soup of anthrax proteins, is alleged to have caused significant side-effects among the thousands of US military personnel who got mandatory anthrax vaccination.
In other developments, Dugway Proving Ground in Utah, a major biodefence lab for the US Army, has admitted that it has been producing weaponised, powdered anthrax, of the sort used in the attacks, since 1998. It claims none has gone missing, but will not confirm or deny that it ever weaponised the precise strain being used in the attacks. Dugway is one of five US and UK labs now known to hold that strain.
