Crude and adjusted hazard ratios (HR) from Cox proportional hazards model (based on multiply-imputed data) for influenza-confirmed admissions in children aged 6–23 months (age group 2)
| Crude HR (95% CI) | Adjusted HR (95% CI) | |
| Gestational age | ||
| Preterm (<37 weeks) | 1.95 (1.55–2.46) | 1.36 (1.03–1.80) |
| Term (37–40 weeks) | 1 | 1 |
| Late term (≥41 weeks) | 0.87 (0.73–1.04) | 0.90 (0.75–1.07) |
| Sex | ||
| Male | 1 | 1 |
| Female | 0.81 (0.70–0.93) | 0.82 (0.71–0.95) |
| High-risk condition recorded at age <6 months | ||
| No | 1 | 1 |
| Yes | 3.83 (3.00–4.88) | 3.04 (2.33–3.96) |
| Postnatal stay in hospital | ||
| ≤14 days | 1 | 1 |
| >14 days | 4.04 (2.87–5.68) | 1.82 (1.18–2.80) |
| Season of birth | ||
| January–March | 1 | 1 |
| April–June | 1.20 (1.00–1.45) | 1.21 (1.00–1.45) |
| July–September | 0.78 (0.63–0.96) | 0.78 (0.64–0.96) |
| October–December | 0.77 (0.62–0.95) | 0.77 (0.63–0.95) |
| Number of older siblings (parity) | ||
| 0 | 1 | 1 |
| 1 | 1.09 (0.93–1.29) | 1.18 (0.99–1.40) |
| ≥2 | 1.37 (1.14–1.64) | 1.49 (1.23–1.80) |
| Maternal smoking during pregnancy | ||
| No | 1 | 1 |
| Yes | 1.39 (1.17–1.66) | 1.25 (1.03–1.50) |
| Maternal age group | ||
| <20 years | 1.48 (1.13–1.95) | 1.65 (1.23–2.23) |
| 20–29 years | 1.18 (1.01–1.38) | 1.24 (1.05–1.46) |
| 30–39 years | 1 | 1 |
| ≥40 years | 0.89 (0.58–1.37) | 0.81 (0.53–1.25) |
| SIMD quintile | ||
| 1 (most deprived quintile) | 1.10 (0.87–1.40) | 0.89 (0.69–1.14) |
| 2 | 1.25 (0.99–1.60) | 1.08 (0.84–1.38) |
| 3 | 1.20 (0.94–1.54) | 1.09 (0.85–1.41) |
| 4 | 1.16 (0.97–1.59) | 1.18 (0.92–1.52) |
| 5 (least deprived quintile) | 1 | 1 |
Events n=780; subjects n=399 454. SIMD: Scottish Index of Multiple Deprivation.