Research ArticleAnthrax

Anthrax Vaccine–Induced Antibodies Provide Cross-Species Prediction of Survival to Aerosol Challenge

Science Translational Medicine  12 Sep 2012:
Vol. 4, Issue 151, pp. 151ra126
DOI: 10.1126/scitranslmed.3004073

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Satisfying the Animal Rule

Vaccines have come a long way since the time of Jenner and Pasteur. Yet, the success of vaccination comes with its own costs. Testing new vaccines, especially against high-risk diseases, is increasingly limited to animal models. This is especially true for diseases that are rare yet deadly, such as anthrax. There are clear ethical limits to conducting efficacy trials for an anthrax vaccine in humans. After all, would you want to be the test subject if the vaccine didn’t work? However, these limitations shouldn’t block the development of new vaccines. Indeed, the threat of bioterrorism makes a workable human anthrax vaccine a priority.

To balance the need for new vaccines with the risk of testing, the Food and Drug Administration (FDA) issued an “Animal Rule” in 2002, which allows the approval of new products based on efficacy data in animals combined with immunogenicity and safety data in both animals and humans. Fay et al. now combine the results of 21 studies conducted in different species ranging from rabbit to macaque in a variety of different experimental conditions, including vaccine type and formulation, vaccination schedule, and challenge time. They found that across these studies, a lethal toxin neutralization activity assay (TNA) correlated with survival. They propose that this TNA can function as an immunological bridge to predict vaccine efficacy in humans. These data are a step toward satisfying the FDA’s Animal Rule and may pave the way for the approval of an anthrax vaccine in humans.