1. Department of Pediatrics, Division of Infectious Diseases, Kaiser Permanente Medical Center, Lancaster, CA, USA
2. Department of Pediatrics, Division of Infectious Diseases, California Pacific Medical Center, San Francisco, CA, USA
3. Department of Biostatistics, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
4. Department of Pediatrics, Division of Infectious Diseases, Mattel Children's Hospital at UCLA, Los Angeles, CA, USA
5. Department of Pediatrics, Division of Infectious Diseases, Duke Children's Hospital, Durham, NC, USA