Influenza B virus reverse genetic backbones with improved growth properties in the EB66® cell line as basis for vaccine seed virus generation.

•These are the initial steps of optimizing influenza B virus growth within the EB66 cell line.•A collection of 71 influenza B viruses were curated and sequenced, some reported for the first time.•Potential vaccine backbones from the top growing influenza B viruses using reverse genetics.•We show that known chemical influenza virus growth enhancers are functional in the EB66 cell line.