Influenza vaccination for patients with chronic obstructive pulmonary disease: understanding immunogenicity, efficacy and effectiveness.

Influenza infection is an important cause of global mortality and morbidity with the greatest impact on older people and those with chronic disease. Patients with chronic obstructive pulmonary disease (COPD) are particularly vulnerable to influenza, with evidence for increased incidence and severity of infection. In this patient group influenza is associated with exacerbations and pneumonia which result in a significant healthcare burden and premature mortality. Influenza vaccination and in particular the use of the seasonal trivalent influenza vaccine (TIV) is recommended for patients with COPD. The evidence base for its effects in this population is, however, limited. Available data suggest that immunogenicity is variable in COPD but the underlying mechanisms are not completely understood. The contribution of age, disease severity, comorbidity and treatments to vaccine responses has only been investigated in a limited manner. Existing data suggest that key immune mechanisms governing T- and B-cell responses are adversely affected by these factors. The efficacy of TIV has been studied in a number of small clinical trials which form the basis of a Cochrane review. Here evidence for effect is conflicting depending on individual trial design and inclusions. Overall, TIV offers protection against influenza infection in the trial setting but further studies are required to stratify patients and enable prediction of inadequate responses. Larger-scale clinical studies have largely been observational and have often been conducted in consort with pneumonia vaccination. Overall the mortality benefit of TIV in COPD is suggested by a number studies but the impact on exacerbation prevention is less clear. Influenza vaccination currently plays an important role in disease prevention in COPD. However, we postulate that a more in-depth understanding of mechanisms of response in the context of a highly heterogeneous disease will lead to a more informed approach to vaccination and greater benefit for the individual patient.