A growing number of patients with Crohn's disease are treated with immunosuppressive agents, such as anti-tumor necrosis factor blockers and immunomodulators. Several recent studies have indicated that immunosuppressive treatment may impair the immunological response to pneumococcal vaccination in patients with inflammatory bowel disease (Crohn's disease and Ulcerative colitis). One of weaknesses in the previous studies did not focus on specific disease, such as Crohn's disease. In addition, predictive factors affecting impaired response following pneumococcal vaccination have not clearly evaluated in patients with Crohn's disease. In this study, patients with Crohn's disease will be assessed for serological response to pneumococcal vaccination. Further, potential predictive factors that impact on vaccination outcomes and adverse events related to vaccination will be evaluated.

Inclusion Criteria:

• Patients over the age of 18
• Informed consent
• Patients who had a definitive diagnosis of Crohn's disease for more than 6 months (documented by the standard clinical, radiographic, endoscopic, and histopathologic criteria)

Exclusion Criteria:

• Hypersensitivity to any component of the pneumococcal vaccine
• Known allergy to pneumococcal vaccination
• Patients who treated with glucocorticoids (prednisolone > 20 mg/day equivalent for 2 weeks or more, and within 3 months of stopping
• Patients who inoculate another vaccine in the past 4 weeks
• Significant protein calorie malnutrition
• Current signs or symptoms of severe, progressive or uncontrolled renal, hepatic, hematologic, endocrine, pulmonary, cardiac, infectious, neurologic or cerebral disease
• Any condition which, in the opinion of the Investigator, places the patient at unacceptable risk if he/she were to participate in the study