Whether the vaccine works against inhalation anthrax is another question. Although five cases of inhalation anthrax occurred during the 1970 test, none of the victims of the disease had been vaccinated. But there were too few cases to determine whether it was effective against inhaled anthrax. Today, the rarity of the disease and the practical elimination of a domestic wool mill industry makes further clinical studies impossible. Instead, researchers test the vaccine with animals, which are then exposed to aerosolized anthrax.
Results are less impressive with some other animals.
Nass points to Army studies that show only 23 percent to 71 percent of guinea pigs survived when exposed to aerosolized anthrax after vaccination. Mice survived at even lower rates. Test results, says Friedlander, depend on the animal and the particular strain of anthrax used. Eight of the 32 strains tested on the guinea pigs overcame the vaccine. But Friedlander says the guinea pig isn't as reliable a predictor of human reaction.