Our primary objectives are to determine whether vitamin D supplementation reduces the risk of acute exacerbations of chronic obstructive pulmonary disease (AECOPD) requiring systemic corticosteroids, antibiotics or both.

Our secondary objectives are to evaluate the impact of vitamin D supplementation on other effectiveness outcomes, including severe AECOPD, i.e. those requiring emergency department (ED) attendance or hospitalisation, moderate AECOPD, study-defined AECOPD, adverse events, death, symptom control, industrial absenteeism, self-reported short-acting bronchodilator use, quality of life; physiological and biochemical, including lung function, exercise tolerance, muscle strength, biomarkers of inflammation, cost-effectiveness and safety in people with COPD.