Effectiveness of Influenza vaccination in reducing disease severity in patients with influenza who were admitted to hospital for the current and any previous season
| Analysis subset | No. of patients with severe influenza (% vaccinated) | No. of patients with nonsevere influenza (% vaccinated) | Crude OR (95% CI) | Adjusted OR (95% CI)* |
|---|---|---|---|---|
| Primary analysis | 130 (28.5) | 598 (48.7) | 0.41 (0.26–0.65) | 0.45 (0.26–0.76) |
| Influenza season | ||||
| 2013/14 | 78 (26.9) | 355 (47.0) | 0.38 (0.21–0.69) | 0.35 (0.17–0.74) |
| 2014/15 | 52 (30.8) | 243 (51.0) | 0.47 (0.23–0.97) | 0.69 (0.28–1.72) |
| Type of influenza virus | ||||
| A/H1N1pdm09 | 79 (21.5) | 246 (44.3) | 0.38 (0.20–0.71) | 0.31 (0.13–0.71) |
| A/H3N2 | 34 (32.4) | 222 (51.4) | 0.39 (0.17–0.89) | 0.32 (0.12–0.89) |
| Sex | ||||
| Female | 64 (18.8) | 279 (46.2) | 0.26 (0.13–0.53) | 0.27 (0.11–0.67) |
| Male | 66 (37.9) | 319 (50.8) | 0.59 (0.32–1.07) | 0.63 (0.30–1.31) |
| Age, yr | ||||
| 65–79 | 71 (26.8) | 340 (42.6) | 0.42 (0.23–0.76) | 0.43 (0.20–0.91) |
| ≥ 80 | 59 (30.5) | 258 (56.6) | 0.42 (0.21–0.83) | 0.42 (0.17–1.02) |
| Major chronic conditions† | ||||
| None | 14 (35.7) | 76 (36.8) | 0.74 (0.22–2.51) | 0.40 (0.03–5.37) |
| Any | 116 (27.6) | 522 (50.4) | 0.38 (0.23–0.62) | 0.39 (0.22–0.69) |
| Pulmonary disease | 55 (36.4) | 262 (53.4) | 0.52 (0.27–1.03) | 0.54 (0.23–1.23) |
| Diabetes | 48 (22.9) | 187 (48.1) | 0.30 (0.14–0.67) | 0.27 (0.08–0.84) |
| Cardiovascular disease | 62 (25.8) | 162 (45.1) | 0.42 (0.21–0.85) | 0.31 (0.12–0.80) |
| Barthel Index score | ||||
| ≥ 40 | 114 (28.9) | 548 (49.3) | 0.42 (0.26–0.68) | 0.49 (0.28–0.87) |
| < 40 | 16 (25.0) | 50 (42.0) | 0.38 (0.09–1.55) | 0.04 (0.00–1.55) |
| Timing of hospital admission | ||||
| < 7 d since symptom onset | 110 (26.4) | 465 (47.1) | 0.39 (0.24–0.65) | 0.40 (0.22–0.73) |
| ≥ 7 d since symptom onset | 20 (40.0) | 133 (54.1) | 0.56 (0.19–1.59) | 0.87 (0.18–4.24) |
| Pneumococcal vaccination‡ | ||||
| Vaccinated | 19 (63.2) | 127 (67.7) | 2.09 (0.25–17.31) | 1.00 (0.06–15.90) |
| Not vaccinated | 111 (22.5) | 471 (43.5) | 0.37 (0.22–0.62) | 0.39 (0.22–0.70) |
| Antiviral treatment | ||||
| Patient treated | 119 (28.6) | 521 (48.6) | 0.44 (0.27–0.71) | 0.50 (0.28–0.90) |
| Patient not treated | 10 (30.0) | 65 (46.2) | 0.35 (0.08–1.56) | NA |
Note: CI = confidence interval, OR = odds ratio, NA = not available.
↵* Estimates obtained from unconditional logistic regression models were adjusted for sex, age, number of chronic conditions, Barthel Index score, number of visits to primary care and hospital in the previous year, pneumococcal vaccination, pneumonia diagnosis in the previous 2 years, treatment with corticosteroids administered orally in the previous month, influenza season and hospital site.
↵† Chronic diseases that were present at baseline, including pulmonary disease, renal disease, diabetes, immunocompromising conditions, neurologic disease, cancer, chronic liver disease, body mass index ≥ 40 kg/m2, cardiovascular disease, neuromuscular disease, cognitive dysfunction and rheumatologic disease.
↵‡ Pneumococcal vaccination with 23-valent polysaccharide vaccine in the previous 5 years or with 13-valent conjugate vaccine.