University of California, San Francisco (UCSF), University of Pennsylvania - Children's Hospital of Philadelphia, Department of Biostatistics and Informatics, University of Colorado, Colorado School of Public Health, Children's Hospital Colorado, Department of Pediatrics, Section of Pulmonary Medicine, University of Colorado School of Medicine, University of Utah, Department of Pediatrics, Section of Critical Care Medicine, University of Colorado School of Medicine and Children’s Hospital Colorado, Department of Pediatrics, Section of Critical Care Medicine, University of Colorado School of Medicine and Children’s Hospital Colorado, Department of Pediatrics, Section of Critical Care Medicine, University of Colorado School of Medicine and Children’s Hospital Colorado, University of Pennsylvania - Children's Hospital of Philadelphia, University of California, San Francisco (UCSF) - UCSF Medical Center, Nationwide Children’s Hospital, University of Pennsylvania - Children's Hospital of Philadelphia, University of Pittsburgh, affiliation not provided to SSRN, University of California, Los Angeles (UCLA) - Department of Pediatrics, Department of Pediatrics, Children’s National Medical Center and George Washington School of Medicine and Health Services, University of California, San Francisco (UCSF), Princeton University, University of California, San Francisco (UCSF) - Division of Infectious Diseases and Children's Hospital Colorado