[1] Childrens Hosp Philadelphia, Pediat Generalist Res Grp, Div Gen Pediat, Philadelphia, PA USA
[2] Childrens Hosp Philadelphia, Div Emergency Med, Philadelphia, PA USA
[3] Childrens Hosp Philadelphia, Dept Pediat Infect Dis, Philadelphia, PA USA
[4] Univ Penn, Sch Med, Ctr Clin Epidemiol & Biostat, Philadelphia, PA USA
[5] Leonard Davis Inst Hlth Econ, Philadelphia, PA USA