[1] Heim Pal Natl Paediat Inst, Budapest, Hungary
[2] Poznan Univ Med Sci, Dept Prevent Med, Poznan, Poland
[3] Univ Hosp Ctr, Dept Paediat, Zagreb, Croatia
[4] Riga Stradins Univ, Dept Paediat, Riga, Latvia
[5] Vilnius Univ, Fac Med, Inst Clin Med, Clin Childrens Dis, Vilnius, Lithuania
[6] Vilnius Univ Hosp Santaros Klinikos, Vilnius, Lithuania
[7] Univ Med Ctr Ljubljana, Dept Infect Dis, Ljubljana, Slovenia
[8] Med Univ Sofia, Hosp Infect Dis, Sofia, Bulgaria
[9] Vilnius Univ, Fac Med, Inst Clin Med, Clin Infect Dis & Dermatovenerol, Vilnius, Lithuania
[10] Univ Med & Pharm Iuliu Hatieganu, Mother & Child Care Dept, Cluj Napoca, Romania
[11] Slovak Med Univ, Fac Publ Hlth, Bratislava, Slovakia
[12] Comenius Univ, Jessenius Fac Med Martin, Bratislava, Slovakia
[13] Univ Zagreb, Sch Med, Univ Hosp Infect Dis, Zagreb, Croatia
[14] MSD Polska Sp Zoo, Global Med Affairs, Warsaw, Poland
[15] Merck & Co Inc, Ctr Observat & Real World Evidence CORE, Kenilworth, NJ 07033 USA