1. Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
2. Division of Biostatistics and Epidemiology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA
3. RTI International, Research Triangle Park, North Carolina, USA
4. Rescue Agency, San Diego, California, USA
5. Department of Epidemiology, College of Public Health, University of Kentucky, Lexington, Kentucky, USA