[1] Stanford Univ, Dept Pediat, Stanford, CA 94305 USA
[2] Stanford Univ, Stanford LPCH Vaccine Program, Stanford, CA 94305 USA
[3] Stanford Univ, Stanford Ctr Digest Dis, Stanford, CA 94305 USA
[4] GlaxoSmithKline, Collegeville, PA USA
[5] Stanford Univ, Dept Radiol, Stanford, CA 94305 USA