Table 3.
Non-adjusted and adjusted 2010–2011 seasonal influenza vaccine effectiveness (IVE) to prevent influenza-related hospitalizations.a
| Group at risk | Cases vaccinated |
Controls vaccinated |
IVE (95%CI) Non-adjusted | IVE (95%CI) adjustedb | ||
|---|---|---|---|---|---|---|
| n/N (%) | n/N (%) | |||||
| All (≥18 years old or older) | 37/102 | (36.3) | 77/116 | (66.4) | 71.2% (48.2–84.0%) | 53.9% (11.4–76.0%) |
| All with at least one HRC | 33/79 | (41.8) | 71/104 | (68.3) | 66.7% (37.2–82.3%) | 53.4% (4.1–77.3%) |
| 60 years or older | 30/58 | (51.7) | 75/103 | (72.8) | 60.0% (20.1–80.0%) | 58.5% (16.1–79.4%) |
| 60 years or older with at least one HRC | 28/51 | (54.9) | 70/96 | (72.9) | 54.8% (6.5–78.1%) | 53.7% (3.6–77.8%) |
HRC: High-risk condition.
Cases (influenza positive) and controls (positive for other than influenza respiratory virus).
Adjusted estimates were obtained by stepwise logistic regression selection, P for exclusion ≥0.1, with all relevant covariates included in the model. VE: vaccine effectiveness: (1 − odds ratio) × 100. Variables remaining in the model by group at risk analysis: (a) All: age, epidemiological week and number of general practitioner consultations in the last three months consultations; (b) All with high risk conditions: age, epidemiological week and number of general practitioner consultations in the last three months consultations; (c) Sixty years old or older: never smoker and social class; (d): Sixty years old or older with high risk conditions: never smoker.