Table 4.
Relative risk of selected underlying conditions, associated respiratory infections, hospitalization, in‐hospital complications, length of hospital stay, and mortality, among patients infected with different influenza virus types, subtypes, and lineages
| First author, y | Setting | Age group or range | Underlying conditions | Associated respiratory infections | Hospitalization, in‐hospital complications, length of hospital stay, and mortality | Age‐adjusted |
|---|---|---|---|---|---|---|
| A vs B | ||||||
| Hite, 2007 40 | Non‐hosp | <19 | ‐ | URTI: nr & ns | Hospitalization: nr & ns | Unclear |
| LRTI: nr & ns | Mechanical ventilation: nr & ns | |||||
| Length of hospital stay: nr & ns | ||||||
| Death: nr & ns | ||||||
| Irving, 2012 8 | Non‐hosp | All ages | ‐ | Pneumonia: 1.2 (0.5‐2.8) | Hospitalization: 1.2 (0.7‐2.4) | Yes |
| A(H1N1)p vs B | ||||||
| Gutiérrez‐Pizarraya, 2012 41 | Non‐hosp | >14 | Chronic cardiovascular disease: 1.1 (0.4‐3.1) | Pneumonia: 1.5 (0.7‐3.3) | Hospitalization: 1.6 (0.8‐3.3) | Unclear |
| Chronic respiratory disease: 1.1 (0.5‐2.4) | ICU admission: 1.9 (0.6‐5.7) | |||||
| Diabetes mellitus: 0.2 (0.04‐1.2) | Mechanical ventilation: 1.2 (0.4‐3.7) | |||||
| Chronic renal disease: 0.8 (0.3‐2.8) | Death: 1.7 (0.6‐5.2) | |||||
| Obesity: 0.9 (0.4‐2.3) | ||||||
| Dawood, 2011 19 | Hosp | ≤17 | Any underlying condition: 2.0 (1.4‐3.1) | Pneumonia: 1.3 (0.8‐2.0) | ICU admission: 1.6 (0.9‐2.8) | Unclear |
| A(H3N2) vs B | ||||||
| Chaves, 2013 9 | Hosp | <18 | ‐ | ‐ | ICU admission or death: 1.01 (0.56‐1.82) | Yes |
| Chaves, 2013 9 | Hosp | Adults | ‐ | ‐ | ICU admission or death: 0.91 (0.65‐1.27) | Yes |
| Wie, 2013 44 | Non‐hosp | Adults | ‐ | ‐ | Hospitalization: 1.19 (0.59‐2.40) | Yes |
| Cohen, 2014 30 | Hosp | All ages | Any underlying condition: nr & ns | ‐ | ICU admission: nr & ns | |
| Mechanical ventilation: nr & ns | ||||||
| Oxygen supplementation: nr & ns | ||||||
| Length of hospital stay: 0.62 (0.45‐0.83) | ||||||
| Death: nr & ns | ||||||
| A(H1N1) vs A(H1N1)p | ||||||
| Esposito, 201112 | Non‐hosp | <14 | ‐ | URTI: 0.88 (0.66‐1.16) | Hospitalization: 0.82 (0.59‐0.97) | Yes |
| LRTI: 0.62 (0.39‐0.99) | Length of hospital stay: 0.18 (0.06‐0.56) | |||||
| A(H1N1) vs A(H3N2) | ||||||
| Esposito, 201112 | Non‐hosp | <14 | ‐ | URTI: 0.75 (0.50‐1.14) | Hospitalization: 0.70 (0.51‐0.96) | Yes |
| LRTI: 0.59 (0.37‐0.93) | Length of hospital stay: 0.41 (0.15‐0.65) | |||||
| A(H1N1)p vs A(H3N2) | ||||||
| Esposito, 201112 | Non‐hosp | <14 | ‐ | URTI: 0.86 (0.43‐1.76) | Hospitalization: 0.96 (0.64‐1.72) | Yes |
| LRTI: 0.79 (0.55‐1.11) | Length of hospital stay: 1.22 (1.03‐1.97) | |||||
| Chaves, 2013 9 | Hosp | <18 | ‐ | ‐ | ICU admission or death: 2.19 (1.11‐4.33) | Yes |
| ≤18 | ‐ | ‐ | ICU admission or death: 2.21 (1.66‐2.94) | Yes | ||
| Dangi, 2014 10 | Non‐hosp | All ages | Any underlying condition: nr & ns | ‐ | Unclear | |
| Cohen, 2014 30 | Hosp | All ages | Any underlying condition: nr & ns | ‐ | ICU admission: nr & ns | Yes |
| Mechanical ventilation: nr & ns | ||||||
| Oxygen supplementation: nr & ns | ||||||
| Length of hospital stay: nr & ns | ||||||
| Death: nr & ns | ||||||
| Kusznierz, 2016 33 | Hosp | All ages | ‐ | ‐ | ICU admission or death: 2.6 (1.0‐6.8) | Yes |
| B Victoria vs B Yamagata | ||||||
| Dangi, 2014 10 | Non‐hosp | All ages | Any underlying condition: nr & ns | ‐ | ‐ | Unclear |
| Sočan, 2014 31 | Non‐hosp | All ages | Chronic cardiovascular diseases: 0.8 (0.2‐2.7) | Pneumonia: 0.8 (0.2‐3.1) | ‐ | Yes |
| Chronic respiratory diseases: 1.6 (0.1‐17.2) | Bronchitis: 1.2 (0.4‐3.4) | |||||
| Diabetes mellitus: 0.7 (0.2‐2.7) | ||||||
| Chronic renal diseases: 1.3 (0.3‐6.0) | ||||||
| Obesity: 1.1 (0.2‐6.1) | ||||||
ns, not statistically significant; nr, not reported; Hosp, hospital‐based studies; Non‐hosp, non‐hospital‐based studies; ICU, intensive care unit; LRTI, lower respiratory tract infection; URTI, upper respiratory tract infection. Bold value indicates the significant findings (p < .05).