[Effectiveness of influenza vaccination in preventing hospital admission due to exacerbations of chronic obstructive pulmonary disease].

Introduction: The main objective was to determine the effectiveness of influenza vaccination in preventing hospitalization due to exacerbation of chronic obstructive pulmonary disease (COPD). One secondary objective was to estimate the prevalence of vaccination, and to describe the factors that were associated with being vaccinated.

Methods: A retrospective cohort study was conducted that included 1,323 patients diagnosed with COPD in the Health Centre of the Pla d'Urgell (Lleida, Spain). They were classified into two cohorts: cohort1, patients vaccinated against seasonal influenza (campaign 2011/12), and cohort2, non-vaccinated. The number of patients in both cohorts requiring hospital admission for exacerbation of the disease between the 12/01/2011 and the 03/15/2012 was quantified. Information about the variables of interest was recorded for each patient. A univariate and multivariate analysis was performed. The effectiveness of vaccination was calculated with the formula: E=(1-OR)×100. The ORs and their 95% confidence interval (95%CI) were determined by multivariate logistic regression models.

Results: Just over half (55.3%) of the patients had been vaccinated. Vaccinated patients were older and had more associated comorbidity. At the same time, they were less hospitalized (3.0% versus 8.9%; P=.001). The crude and adjusted effectiveness of influenza vaccination in this population subgroup was 68.4% (95%CI: 47.5-81.0) and 90.8 (95%CI: 96.8-88.2), respectively.

Conclusion: Influenza vaccination is effective in preventing hospitalization due to acute exacerbations in COPD patients. However, immunization coverage is not as high as desired. Designing programs to increase the rate of vaccination in this population would reduce the number of hospital admissions for COPD exacerbation.