MCRF scientists Ed Belongia, MD, and Huong McLean, PhD were among 45 scientists worldwide invited to attend an international symposium hosted by the British Columbia Centre for Disease Control to discuss influenza repeat vaccination effects (I-ReV). Since the 1970s, there has been controversy about the effects of repeated influenza vaccination, and recent studies have raised new questions about the impact of annual vaccination and vaccine-induced protection. The I-ReV symposium brought together academic researchers and government agencies to identify gaps in knowledge, discuss the complex relationship between virus evolution, vaccine antigens, and immune response, and consider new research and strategies to enhance protection. The participants included epidemiologists, virologists, immunologists, and systems biology experts from North America, Europe, and Australia. The cross-disciplinary discussions led to new insights and research priorities, and a summary of the meeting is being prepared for publication. Dr. Belongia was a member of the symposium planning committee and presented an overview of repeat vaccination effects, including research led by Huong McLean at MCRF.