Effect of viral membrane fusion activity on antibody induction by influenza H5N1 whole inactivated virus vaccine

► Formaldehyde treatment blocks fusion activity of WIV. ► Fusion inactivation of WIV reduces, but not block, TLR7-dependent IFNα induction. ► Fusion inactivation does not block WIV-induced IgG2c responses. ► Antibody affinity maturation is not affected by fusion inactivation of WIV.