American Anthrax
Vaccine Can Be Defeated

From Eric Howarth
Biological warfare experts are concerned that countries like Iraq may be able to create forms of anthrax that can overcome the vaccine now being given to American troops in the Persian Gulf.
The concern stems from recent evidence that the Soviet Union may have mixed together several strains of anthrax, presumably to enhance the lethality of its germ weapons. Further questions have been raised by separate reports that Russian scientists have produced strains of anthrax genetically engineered to produce new toxins.
Any country with a modern microbiology laboratory could perform these manipulations, although experts differ over how effective they would be in producing a germ weapon that could thwart the American vaccine.
The vaccination program, under which all 2.4 million American military personnel are eventually to be immunized, has been criticized by Citizen Soldier, an advocacy group for veterans, which says the vaccine's efficacy is unproved. Given the risk of side effects, the group argues, the vaccine should not be administered.
Army experts and other scientists say the vaccine is effective, although much of the evidence is necessarily indirect, since battlefield anthrax cannot ethically be tested on people. They also believe that the vaccine cannot be circumvented by use of multiple anthrax strains.
Anthrax is a biological weapon of choice because the bacillus forms a sturdy, long-lasting spore and is deadly when inhaled unless antibiotics are given immediately. It is one of the agents Iraq is known to have had in its arsenal.
The American vaccine has protected people who handle goat and sheep wool from cutaneous anthrax, the usually nonlethal form of the disease that attacks the skin. But its efficacy against inhalation anthrax, the form that would threaten troops on the battlefield, is harder to assess.
Experts agree that the vaccine is not perfect. "The protective efficacies of both the U.K. and U.S. vaccines are less than ideal," a British anthrax expert, Dr. Peter C.B. Turnbull, wrote in 1991. The vaccine was first licensed in 1970, and its design has not changed since. But it is the only anthrax vaccine that is available and approved by the Food and Drug Administration.
The vaccine's defenders say it has a long record of safety and effectiveness. There are no permanent side effects of any kind, and only some 2 to 4 percent of those immunized experience significant local reactions at the injection site, said Dr. Arthur M. Friedlander, chief bacteriologist at the Army Medical Research Institute of Infectious Diseases, at Fort Detrick, Md.
Studies show that the vaccine defends only 20 percent of guinea pigs against airborne anthrax spores, a point emphasized by Citizen Soldier. But, Friedlander said, it protects more than 95 percent of rhesus monkeys, which are more similar to humans. In tests, the vaccinated monkeys survive even when given doses of anthrax that are hundreds of times greater than the amount that kills 50 percent of an unprotected population.
The only time the vaccine has been tested against inhalation anthrax in humans was among mill workers in the early 1960s, when the disease was still common in the United States. Only five cases of inhalation anthrax occurred among the workers during the study period, none of them among those vaccinated. But the numbers were not large enough to prove in a statistically meaningful way that the vaccine was effective against inhaled anthrax spores, the authors of the study wrote.
Even if the vaccine is effective against ordinary anthrax, some critics of the Army's policy are concerned that an adversary could manipulate the bacillus so as to overwhelm the it. "One would have to be a fool to believe Iraq could not make a strain resistant to the vaccine," said Dr. Meryl Nass, a physician who advises Citizen Soldier.
Concern that the vaccine can be sidestepped has been fanned by recent news of Russian activities. In 1979 an accident at a Soviet biological warfare center killed some 70 people in the city of Sverdlovsk, now Ekaterinburg. From autopsy tissues that came into American hands, scientists led by Dr. Paul J. Jackson of the Los Alamos National Laboratory inferred this January that at least four strains of anthrax had been present. The purpose of such a mixture, Jackson suggested, might have been to overwhelm the American vaccine.
That vaccine works by disabling a component of anthrax known as protective antigen, which helps the microbe's two toxins penetrate the cells they are attacking. Friedlander said all known strains of anthrax share the same basic form of protective antigen. For this reason, he said, the vaccine should be equally effective against any combination of strains.
It is relatively easy to make bacteria resistant to antibiotics. But, Friedlander said, it is quite difficult to alter the protective antigen without making the anthrax bacillus ineffective as a weapon. So the United States' defensive strategy against anthrax has always focused on having a good vaccine.
Russian scientists recently caused consternation by reporting at a scientific conference that they had made an anthrax strain resistant to antibiotics. But, American officials say, there was a benign explanation for the research. Russia relies on a vaccine made from a live but nonlethal strain of the anthrax bacterium. Making the vaccine strain resistant to antibiotics, which would otherwise kill it, would allow physicians to give the vaccine and antibiotics simultaneously to anyone exposed to anthrax. (The American vaccine does not contain live bacteria.)
Western experts have found it harder to find innocent explanations for a second Russian experiment, published recently in the journal Vaccine.
The experiment involved inserting toxin-making genes from a closely related and usually harmless microbe, Bacillus cereus, into the Russian vaccine strain. The apparent purpose was to create a vaccine effective against a natural anthrax strain that produced these toxins. No such strain is known to exist.
The Russian scientists, who work at the Obolensk State Research Center for Applied Microbiology, near Moscow, reported that this engineered strain of anthrax killed hamsters that had received the ordinary Russian vaccine.
Friedlander said there was no way of knowing whether the American vaccine would protect against such a genetically changed organism, which probably kills by a different mechanism.
But he said it was also far from clear that this organism could be developed into a weapon that would kill people after being inhaled. The Russian research, Friedlander said, showed only that the engineered organism killed hamsters after injection.

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