[1] Harvard Univ, Childrens Hosp, Sch Publ Hlth, Div Infect Dis, Boston, MA 02115 USA
[2] Harvard Univ, Sch Publ Hlth, Dept Epidemiol, Boston, MA 02115 USA
[3] Harvard Univ, Sch Publ Hlth, Dept Immunol & Infect Dis, Boston, MA 02115 USA
[4] Radboud Univ Nijmegen, Med Ctr, Lab Pediat Infect Dis, Dept Pediat, NL-6525 ED Nijmegen, Netherlands
[5] Spaarne Hosp, Dept Pediat, Hoofddorp, Netherlands
[6] Univ Med Ctr Utrecht, Dept Pediat Immunol & Infect Dis, Utrecht, Netherlands
[7] Univ Manitoba, Infect Dis Sect, Winnipeg, MB, Canada