||Vaccines contribute to improved animal and human health and welfare by preventing diseases and deaths from infectious diseases. However, testing necessary to ensure vaccine effectiveness and safety can involve large numbers of animals and significant pain and distress. NICEATM and ICCVAM recently convened an international workshop to review the state of the science of available alternative methods and approaches that can further reduce, refine, and replace the use of animals for human and veterinary vaccine potency and safety testing, and to identify research, development, and validation efforts necessary to further advance new and improved alternative methods. Workshop participants identified human and veterinary vaccines that should have the highest priority for future efforts. Prioritization criteria included testing that involves significant pain and distress, large numbers of animals, and pathogens that are dangerous to people and animals. Participants noted that in vitro antigen quantification assays have replaced animals for potency testing for some killed vaccines, and recommended that this approach be expanded to other vaccines. Recommendations to support more humane animal use included development and use of humane endpoints for all challenge tests, development of serologic assays to replace challenge tests, and development of in vitro toxin neutralization tests (TNT) to replace in vivo TNTs. Workshop participants recommended several approaches that might further reduce the number of animals required for specific potency tests. Participants also recommended priority vaccines for which alternative safety testing methods should be pursed and that would have the greatest impact on avoiding pain and distress and reducing animal numbers. Finally, workshop participants recommended enhanced international harmonization and cooperation efforts and closer collaborations between human and veterinary researchers to expedite progress. Implementation of the workshop recommendations is expected to advance new methods for vaccine testing that will reduce animal use, benefit animal welfare, and ensure continued and improved protection of human and animal health.