Over-anxious over anthrax

by Howard Fienberg
January 10, 2002

In the USA, postal workers, congressional staff and some journalists have been exposed to anthrax-laced mail over the past three months. The anthrax vaccine is available for their use - but they fear the consequences of the vaccine almost as much, if not more than, anthrax itself. And now that people must sign consent forms, their fears are being reinforced.

So can the vaccine be administered safely? Will it be effective at this point? The first question is much easier to answer than the second.

The US Food and Drug Administration (FDA) licensed the vaccine in 1970 for civilians, to protect us against possible infection by anthrax bacteria. It has been in use for decades, primarily for veterinarians and those who work with animal hides and wool, as well as scientists who study anthrax. The US military started administering the vaccine in the 1990s and has so far inoculated at least 524,000 military personnel. Surveillance data shows some adverse side-effects, but most are mild and short term - like swelling, aches and fever, similar to the side effects caused by many other vaccinations.

The FDA formally classifies the anthrax vaccine as 'experimental' because of continuing problems at the facilities of BioPort, the Michigan-based company that is currently the vaccine's only producer. But the problems appear to be procedural rather than scientific; and probably will not impact on the vaccine.

No credible scientific evidence points to long-term harm from the anthrax vaccine. Individual soldiers, usually not trained medical personnel, have been prone to the post-hoc fallacy: 'I got ill some time after I got my shots, therefore the shots must have caused my illness.' One serviceman told a 60 Minutes episode that 'it's not a matter of what I think. My body told me that the shot was not good for me'. While intuition may be a powerful motivator, it provides no substitute for science.

So the vaccine appears to be safe, but will it work? That is a much tougher question. Studies have shown the vaccine to be effective protection against anthrax exposure - but there is little way to know whether it can help those who have already been exposed to anthrax, because the vaccine was never tested for that use. Vaccines are designed for pre-exposure, not post-exposure.

However, with rising concerns about antibiotic resistance, the vaccine may be an important route to pursue. Bacteria might become resistant following prolonged exposure to low doses of certain kinds of antibiotics, like Cipro.

Though even the US Centers for Disease Control and Prevention admit that no vaccine is 100 percent safe, the fatal effects of anthrax probably outweigh any possible (and as yet undiscovered) long term ill-effects of the anthrax vaccine. Nobody can say for certain that the vaccine will help much post-exposure - but we can say that it probably won't hurt. If I were exposed to anthrax, I would take the vaccine.

Does that mean that everybody should run out and get vaccinated? Of course not. Vaccine supplies are limited. People facing anthrax exposure need to weigh the possible risks of the vaccine, but people who have not been exposed and are unlikely to be exposed, have no need for it anyway.

Howard Fienberg is senior research analyst with the non-profit non-partisan think-tank the Statistical Assessment Service (STATS), in Washington, DC.

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