1 Keck School of Medicine, University of Southern California, Los Angeles, Calif.
2 Biostatistics Core, The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, Calif; Southern California and Clinical Translation Science Institute, University of Southern California, Los Angeles, Calif.
3 Infection Prevention and Control, Children's Hospital Los Angeles, Los Angeles, Calif.
4 Keck School of Medicine, University of Southern California, Los Angeles, Calif; Division of Clinical Immunology and Allergy, Children's Hospital Los Angeles, Los Angeles, Calif. Electronic address: pyong@chla.usc.edu.