CDC, which performed some vaccine tests, acknowledged in 1968 that, "As to the efficacy of the vaccine, we have no real method of determining the protection afforded." FDA records show that in 1969 the ad hoc committee to license anthrax vaccine found a lack of "scientific evidence for efficacy of the vaccine." The committee chairman, Dr. Margaret Pittman, then noted, "Michigan has filed all required information and material for license except the results of an adequately controlled clinical investigation that establishes efficacy." Michigan was asked to conduct such a trial, but there is no evidence it was ever carried out. This demonstrates that the vaccine was never proven effective in humans.
Potency of the vaccine has been a continuous headache for the manufacturers. Many different potency standards have been submitted to FDA over the years. The potency assay kept changing because it could never be demonstrated to accurately reflect the potency of the product. One license amendment for potency was submitted in 1978. More were submitted prior to the first Gulf War. As recently as May 2001 Bioport was still submitting amendments to the potency test.
Therefore, FDA should have pulled the vaccine's license, since anthrax vaccine was unable to meet FDA standards for potency and human efficacy from the time the license was first issued. It means that FDA has never known whether or how much the vaccine will protect against anthrax.