Authorization allowing the Food and Drug Administration (FDA) to strengthen public health protections against chemical, biological, radiological, and nuclear threats including infectious diseases, by facilitating the availability and use of medical countermeasures needed during public health emergencies. Under section 564 of the Federal Food, Drug, and Cosmetic Act, FDA may authorize unapproved medical products or unapproved uses of approved medical products to be used in an emergency to diagnose, treat, or prevent serious or life-threatening diseases or agents when certain criteria are met, including there are no adequate, approved, and available alternatives.(From fda.gov/regulatory-information/search-fda-guidance-documents/emergency-use-authorization-medical-products-and-related-authorities)