Influenza is associated with significant disease burden in the US. Influenza vaccination effectiveness (VE) is low due to several factors, including egg adaptations. Evidence for a relationship between egg-based manufacturing and influenza VE remains largely disassociated, except for two previous European consensuses. The aim of this study was to observe US expert consensus on the phenomenon. Ten US influenza experts assessed evidence for antigenic drift, egg adaptations, and manufacturing component principles of the research question in a novel two-stage online study design to observe proportional group awareness and consensus, known as the Jandhyala Method. US experts agreed that all component principles had a majority of strong or very strong supporting evidence (52–86%), similar to European results (70-90%). They agreed that global surveillance, WHO candidate vaccine virus selection, and manufacturing stages involving eggs were the most likely to impact influenza VE. There was unanimous agreement for a mechanistic basis for reduced influenza VE due to egg-based manufacturing. There is now US and European expert agreement for the increased risk of reduced influenza VE resulting from egg-based manufacturing techniques. Increasing the use of non-egg-based manufacturing that avoids egg-adaptations is a currently available strategy that may improve influenza VE.