Prevalence of Influenza Vaccination in Chronic Obstructive Pulmonary Disease Patients and Impact on the Risk of Severe Exacerbations

Objective: To determine the prevalence of influenza vaccination in chronic obstructive pulmonary disease (COPD) patients, and the effectiveness of the procedure. Methods: Retrospective population-based cohort study. On 31 December 2011, influenza vaccination history was retrieved from 899 patients with confirmed COPD selected by simple random sampling from all COPD patients in Cantabria (northern Spain). Severe exacerbations (hospitalization due to COPD exacerbation) and overall mortality during 2012 were treated as dependent variables. Odds ratios (OR) were estimated by logistic regression, adjusting for age, sex, smoking status, severity of COPD, and frequency of exacerbations during the previous year. Prevented fraction among the exposed (PFe-adjusted) was determined as a measure of impact. Results: Overall prevalence of influenza vaccination was 62.7%, but this rate fell in patients classified as more severe according to FEV1 (52.0%). Influenza vaccination showed a statistically significant protective effect against severe exacerbations in the following year: Ora: 0.54 (95% CI: 0.35-0.84); FPe-adjusted: 0.46 (95% CI: 0.16-0.65). A non-significant protective effect for overall mortality was observed: Ora: 0.76 (95% CI: 0.41-1.40). When stratified according to COPD severity (FEV1), the protective effect against risk of hospitalization was higher in more severe COPD patients: Ora: 0.23 (95% CI: 0.11-0.48); FPe-adjusted: 0.77 (95% CI: 0.52-0.89). Conclusions: We found that influenza vaccination has a protective effect and reduces the risk of hospitalization due to exacerbations in the following year. Despite the evidence for protection, prevalence of vaccination was not optimal, especially in more severe COPD patients. (C) 2015 SEPAR. Published by Elsevier Espana, S.L.U. All rights reserved.