| Principal phenotype Median (mean) | Refined phenotype (age-limited)Median (mean) | |
| Duration of admission (days) | 4 (5.3) | 4 (4.9) |
| Weight on admission (kg) | 5.15 (5.47) | 5.03 (5.18) |
| Age on admission (weeks) | 10 (15.6) | 8 (9.1) |
| RSV positive (%) | 100% | 100% |
| Oxygen used (%) | 88% | 86% |
| Duration of oxygen (days) | 3 (3.78) | 3 (3.6) |
| Tube feeding required (%) | 60.9% | 61.7% |
| Intravenous fluids required (%) | 32.1% | 31.9% |
| Ventilation required (%) | 23.7% | 14.5% |
| Parental smoking (%) | 36.6% | 33.7% |
| Number of older siblings | 1 (1.19) | 1 (1.19) |
| Gestation (weeks) | 39 (38) | 40 (39.4) |
| Pre-existing heart condition (%) | 5.5% | 0.0% |
| Pre-existing lung condition (%) | 5.9% | 0.0% |
| Oxygen-dependent CLD (%) | 2.0% | 0.0% |
CLD, chronic lung disease; RSV, respiratory syncytial virus.