In recent years, widespread emergence of antimicrobial resistance in Streptococcus pneumoniae has became a major global concern, especially in Taiwan, one of the highest levels of antibiotic-resistant pneumococci in the world. Therefore, primary prevention by vaccination is encouraged for those high-risk patients with COPD. The currently available adult pneumococcal vaccine consists of the capsular polysaccharide of 23 different serotypes of Streptococcus pneumoniae (PPSV23). The antibodies produced in response to this polysaccharide can provide protection by inducing host immune cells to kill or to opsonize bacteria for phagocytosis.