[1] Univ Hosp Freiburg, Dept Pediat & Adolescent Med, D-79106 Freiburg, Germany
[2] Robert Koch Inst, D-1000 Berlin, Germany
[3] Univ Dusseldorf, Childrens Hosp, German Pediat Surveillance Unit Off, D-4000 Dusseldorf, Germany
[4] Univ Freiburg, Dept Biometry & Med Stat, Freiburg, Germany
[5] Hannover Med Sch, Perinatal Infect Dis Epidemiol Unit, Dept Obstet, D-3000 Hannover, Germany
[6] Hannover Med Sch, Dept Pediat, D-3000 Hannover, Germany
[7] Childrens Hosp, Dept Neurol, Boston, MA 02115 USA
[8] Harvard Univ, Sch Med, Boston, MA 02115 USA
[9] Univ Munich, Inst Social Pediat & Adolescent Med, Munich, Germany