[1] St Josephs Hosp, Phoenix, AZ 85013 USA
[2] Hosp Ninos Luis Calvo Mackenna, Santiago, Chile
[3] Inst Especializado Salud Nino, Lima, Peru
[4] Univ Arkansas Med Sci, Arkansas Childrens Hosp, Little Rock, AR 72202 USA
[5] Louisiana State Univ, Ctr Med, Shreveport, LA 71130 USA
[6] Columbus Childrens Hosp, Pediat Clin Trials Int, Columbus, OH 43205 USA
[7] Case Western Reserve Univ, Rainbow Babies & Childrens Hosp, Cleveland, OH 44106 USA
[8] Merck Res Labs, West Point, PA 19486 USA