Streptococcus pneumoniae is the most common causes of community-acquired pneumonia and exacerbations in chronic obstructive pulmonary disease (COPD) patients, which are associated with morbidity, mortality, and higher health-care cost. In addition, recently high daily dose of inhaled corticosteroid (ICS) therapy became more evident to be beneficial in moderate-to-severe COPD patients, but excess risk of pneumonia shown in database analysis was worried about by primary physicians. The use of pneumococcal polysaccharide vaccination (PPSV23) has protective efficacy to eliminate infection of Streptococcus pneumoniae from previous studies. If the use of PPSV23 can reduce the incidence of pneumonia or exacerbations in COPD patients using high daily dose of ICS, the benefit of ICS can be preserved and risk of pneumonia can be reduced. However, there is only limited data supporting this hypothesis. In this study, the investigators will conduct a double-blinded, randomized controlled trial to evaluate the clinical efficacy of PPSV23 in severe COPD patients using high daily dose of ICS.