Safety and immunogenicity of revaccination with reduced dose intradermal and standard dose intramuscular influenza vaccines in adults 18-64 years of age.

•Revaccination with intradermal (ID) influenza vaccine was immunogenic and safe.•Previous vaccination with ID vaccine had no impact on intramuscular (IM) vaccination.•Injection site reactions were more frequent with ID vaccine but were well-tolerated.•Safety was more closely linked to the current injection route than the previous route.•Immunogenicity was similar for the ID and IM vaccine groups for all virus strains.