[1] Univ Florence, Dept Pediat, Florence, Italy
[2] Univ Turin, Dept Pediat, I-10124 Turin, Italy
[3] Univ Florence, Dept Stat, Florence, Italy
[4] Bambino Gesu Pediat Hosp, Pediat Clin, Rome, Italy
[5] Univ Milan, Infect Dis Unit, Dept Paediat, L Sacco Hosp, Milan, Italy
[6] Univ Naples Federico II, Dept Pediat, Naples, Italy
[7] Univ Padua, Dept Pediat, Padua, Italy
[8] Univ Milan, Dept Maternal & Pediat Sci, Fdn IRCCS, Osped Maggiore Policlin Mangiagali & Regina Elena, Milan, Italy
[9] Univ Brescia, Pediat Clin, Brescia, Italy
[10] Giovanni XXIII Pediat Hosp, Clin Infect Dis, Bari, Italy
[11] Univ Genoa, Osped San Martino Genova, Infect Dis Clin, Genoa, Italy
[12] Gemelli Hosp, Pediat Intens Unit, Rome, Italy
[13] Univ Bologna, Pediat Clin, S Orsola Hosp, Bologna, Italy
[14] Santa Chiara Hosp, Paediat Unit, Trento, Italy