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U.S. Department of Health and Human Services

Emergency Preparedness and Response

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Animal Rule Q&As


Frequently asked questions about the Animal Rule


What are the hurdles to medical countermeasure development and approval?

A key hurdle is the limited human data available to assess a medical countermeasure's effectiveness.


Why are the data limited?

Most of the diseases or conditions under consideration, like infections such as anthrax, smallpox, and plague, do not occur naturally. If they do occur, the number of people infected is so small that clinical trials are infeasible.

For threats such as radiation or toxic chemicals (e.g., cyanide), accidental exposures can provide limited human data, however, clinical trials to study efficacy are not feasible. It would be unethical to intentionally infect or to expose people to radiation or toxic chemicals to test possible treatments to see if they work.

Then how can a product's effectiveness in people be demonstrated?

Medical product sponsors will have to show that their product works (effectiveness) in studies conducted in animals that model the human disease. Then, FDA will have to rely on these data as substantial evidence of product effectiveness during regulatory decision making.

For many of the threat agents, animal models that simulate critical features of the human disease or condition have not been developed. FDA is encouraging the qualification* of existing models that adequately simulate the human disease or condition and new animal models as they are developed. 

*The guidance defines qualification as a conclusion that within the stated context of use, the “results of assessment with a DDT can be relied on to have a specific interpretation and application in drug development and regulatory decision-making.”

What can be done to address this problem?

FDA is working to:

  • Spur development and evaluation of product-independent animal models for qualification
  • Provide guidance to current and prospective product sponsors on issues related to animal models for medical countermeasures that will be developed under the Animal Rule
  • Make relevant information easily accessible to prospective product sponsors (see Program for Drug Development Tools Qualification)
  • Advance regulatory science to develop tools, standards, and approaches to assess medical countermeasure safety, efficacy, quality, and performance


Have more questions? Email AskMCMi@fda.hhs.gov.