The cumulative probability of survival in the three study groups. Group A: community-acquired pneumonia (CAP) patients with neither acute respiratory failure (ARF) nor severe sepsis (SS) on admission. Group B: CAP patients with only ARF on admission. Group C: CAP patients with both ARF and SS on admission. Adjusted for centers, sex, age, comorbidities (including congestive heart failure, cerebrovascular accident, diabetes, chronic obstructive pulmonary disease, liver and renal diseases), residence in nursing home, multilobar infiltrate, pleural effusion, empiric antibiotic therapy concordant with European respiratory Society guidelines.