This Appendix is intended to provide relevant information for federal and state officials and other interested parties who will participate in making decisions related to vaccination as an aid in controlling an HPAI outbreak in the U.S. The following topics are presented and discussed: Important characteristics of high pathogenicity avian influenza (HPAI); Characteristics of vaccines; Strategies for vaccine use; Various factors that must be considered when designing an effective vaccination program. The United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) Veterinary Services (VS) has a separate document, HPAI Response Plan: The Red Book that identifies the capabilities needed to respond to an HPAI outbreak in the United States as well as identifying all the critical activities involved in responding with the corresponding time-frames. Please refer to that document for those specific details.