Table 1 Inclusion and exclusion criteria for the study

• Patients above 50 years of age, with a prior admission for exacerbation of COPD within the last two years.

• Patients with end-stage COPD, who are not expected to survive for 3 years (typically bedridden patients being dyspnoeic at rest).

• Current or ex-smoker

• Patients with known other respiratory tract infection, e.g. tuberculosis or aspergillosis, in whom the intervention is known to be inefficient.

• Postbronchodilator FEV1 < 60% in stable condition (> 4 weeks after hospitalization)

• Patients with pulmonary malignancy

• < 300 ml bronchodilator reversibility in FEV1

• Patients with other pulmonary diseases than COPD

• Patients with immunodeficiency. However, COPD patients treated with steroids can be included

• Patients with known hereditary disposition to lung infections such as alfa-1-antitrypsin deficiency, cystic fibrosis or primary ciliary dyskinesia.

• Patients receiving long-term antibiotic treatment

• (e.g. recurrent cystitis)

• Patients with known allergy or intolerance to azithromycin

• Pregnant or breastfeeding women

• Manifest heart, liver or renal insufficiency

• Patients that, for reasons not stated above, are unlikely to be able to participate in a study period of 3 years.