Response to 2009 pandemic and seasonal influenza vaccines co-administered to HIV-infected and HIV-uninfected former drug users living in a rehabilitation community in Italy

► Pandemic and seasonal influenza vaccines co-administered to HIV+ and HIV− subjects. ► Immune responses to both vaccinations met the EMA CPMP criteria in both groups. ► 6 months post-vaccination antibody levels decreased in both groups, mainly in HIV+. ► Subjects primed to seasonal influenza had stronger response to pandemic vaccine.