The vaccine was licensed by the F.D.A. in 1970, based on one published study by Brachman et al. During the four year study period there were 26 cases of anthrax, of which twenty-one were cutaneous, and five were due to inhalation. One case occurred in a recipient of the complete vaccine, and two in recipients of the partial vaccine series.
Cutaneous anthrax is amenable to standard therapy and fatal only when septicemia intervenes.
Nor could any estimate be made of the infectious dose. This is particularly important because exposure to anthrax in wartime is likely to involve very high concentrations of the organism, and any vaccine intended for such use must demonstrate efficacy in this setting. There is animal data, however, which provides an indirect and incomplete, yet suggestive idea of vaccine efficacy. Various challenge strains of anthrax were used, although the infectious doses and means by which the animals were exposed were not specified. An abridged summary of his table follows.