Until now, few studies have been designed to specifically examine vaccine efficacy in COPD patients. Among 3 available randomized controlled trials, only one study involving 596 patients found, from post-hoc analyses, some protective efficacy for pneumonia in patients of < 65 years of age and of an FEV1 < 40% predicted. Based on above evidence (only limited body of data), the Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2006 Guideline has recommended the PPSV23 inoculation as evidence B.