Lower respiratory tract infection (LRTI) rates and influenza vaccine effectiveness to prevent LRTI by season (n=190 459)
| Summer | Winter | |||||
|---|---|---|---|---|---|---|
| Influenza vaccination status | Influenza vaccination status | |||||
| >5 years/never | Current | Residual 1–5 years | >5 years/never | Current | Residual 1–5 years | |
| Person-time (years) | 35 233 | 219 456 | 74 704 | 47 352 | 355 766 | 70 718 |
| Infections (n) | 2363 | 22 726 | 8496 | 5751 | 62 077 | 12 900 |
| Crude LRTI rate /1000 py (95% CI) | 73.0 (69.5 to 76.5) | 111.0 (109.2 to 112.9) | 121.3 (118.4 to 124.1) | 134.8 (130.3 to 139.2) | 187.2 (185.4 to 189.4) | 195.5 (191.6 to 199.4) |
| Crude LRTI rate ratio (95% CI) | 1 (ref) | 1.52 (1.45 to 1.60) | 1.66 (1.58 to 1.75) | 1 (ref) | 1.38 (1.34 to 1.44) | 1.45 (1.40 to 1.51) |
| Adjusted* LRTI rate ratio (95% CI) | ||||||
| Overall | 1 (ref) | 1.28 (1.21 to 1.35) | 1.39 (1.32 to 1.47) | 1 (ref) | 1.19 (1.15 to 1.23) | 1.23 (1.18 to 1.28) |
| Stratified by eGFR (mL/min/1.73 m2) | ||||||
| eGFR <30 | 1 (ref) | 1.20 (0.94 to 1.52) | 1.29 (1.01 to 1.65) | 1 (ref) | 1.17 (0.99 to 1.38) | 1.20 (1.01 to 1.43) |
| eGFR 30–44 | 1 (ref) | 1.27 (1.10 to 1.45) | 1.31 (1.13 to 1.51) | 1 (ref) | 1.20 (1.10 to 1.32) | 1.20 (1.08 to 1.33) |
| eGFR 45–59 | 1 (ref) | 1.32 (1.19 to 1.46) | 1.40 (1.26 to 1.56) | 1 (ref) | 1.16 (1.09 to 1.25) | 1.20 (1.12 to 1.30) |
| eGFR ≥ 60 | 1 (ref) | 1.27 (1.19 to 1.37) | 1.42 (1.32 to 1.53) | 1 (ref) | 1.21 (1.15 to 1.27) | 1.26 (1.20 to 1.33) |
| Stratified by proteinuria | ||||||
| No proteinuria | 1 (ref) | 1.27 (1.20 to 1.35) | 1.36 (1.30 to 1.45) | 1 (ref) | 1.18 (1.13 to 1.23) | 1.22 (1.16 to 1.27) |
| Proteinuria | 1 (ref) | 1.33 (1.19 to 1.49) | 1.50 (1.33 to 1.68) | 1 (ref) | 1.23 (1.14 to 1.33) | 1.27 (1.17 to 1.38) |
| Ratio of incidence rate ratios* winter/summer (95% CI) | ||||||
| Overall | 1 (ref) | 0.93 (0.88 to 0.97) | 0.88 (0.83 to 0.93) | |||
| Stratified by eGFR (mL/min/1.73 m2) | ||||||
| eGFR <30 | 1 (ref) | 0.93 (0.73 to 1.17) | 0.90 (0.70 to 1.16) | |||
| eGFR 30–44 | 1 (ref) | 0.88 (0.77 to 1.01) | 0.86 (0.75 to 1.00) | |||
| eGFR 45–59 | 1 (ref) | 0.90 (0.81 to 0.99) | 0.87 (0.78 to 0.98) | |||
| eGFR ≥ 60 | 1 (ref) | 0.95 (0.89 to 1.02) | 0.89 (0.83 to 0.96) | |||
| Stratified by proteinuria | ||||||
| No proteinuria | 1 (ref) | 0.93 (0.88 to 0.99) | 0.90 (0.84 to 0.95) | |||
| Proteinuria | 1 (ref) | 0.90 (0.81 to 1.00) | 0.83 (0.74 to 0.93) | |||
| Vaccine effectiveness (VE)* based on ratio of incidence rate ratios % (95% CI) | ||||||
| Overall | 0 (ref) | 7 (3 to 12) | 12 (7 to 17) | |||
| Stratified by eGFR (mL/min/1.73 m2) | ||||||
| eGFR <30 | 0 (ref) | 7 (−17 to 27) | 10 (−16 to 30) | |||
| eGFR 30–44 | 0 (ref) | 12 (−1 to 23) | 14 (0 to 25) | |||
| eGFR 45–59 | 0 (ref) | 10 (1 to 19) | 13 (2 to 22) | |||
| eGFR ≥ 60 | 0 (ref) | 5 (−2 to 11) | 11 (4 to 17) | |||
| p Value (test for trend)† | – | 0.31 | 0.79 | |||
| Stratified by proteinuria | ||||||
| No proteinuria | 0 (ref) | 7 (1 to 12) | 10 (5 to 16) | |||
| Proteinuria | 0 (ref) | 10 (0 to 19) | 17 (7 to 26) | |||
| p Value‡ | – | 0.56 | 0.26 | |||
*Adjusted for: age, sex, socioeconomic status at practice level, residential care, date post 1 April 2004, smoking status, time-updated comorbidities (ischemic heart disease, congestive cardiac failure, hypertension, cerebrovascular disease, other dementia, chronic lung disease, chronic liver disease), time-updated CKD status (eGFR, proteinuria), steroid use in the 3 months prior to study entry, pneumococcal vaccination, and HbA1C and diabetic medication history at baseline.
†Wald test for interaction of eGFR with influenza vaccination status and season, with eGFR modeled as a linear variable.
‡Wald test for interaction of proteinuria with influenza vaccine and season.
LRTI, lower respiratory tract infection; py, person-years.