[1] Univ Verona, Dept Pathol, Immunol Sect, Specialized Consulting Serv Surveillance Vaccine, I-37100 Verona, Italy
[2] ULSS 5, Dept Prevent, Ovest Vicentino, Veneto Region, Italy
[3] Azienda Osped, Microbiol Virol & Immunol Serv, Verona, Italy
[4] Univ Verona, Dept Neurol & Visual Sci, Neurol Sect, I-37100 Verona, Italy