Epidemiology and risk factors of community-acquired pneumonia in patients with different causes of immunosuppression.

Immunosuppression constitutes a significant risk for community-acquired pneumonia (CAP). Nevertheless, specific causes of immunosuppression and their relevance for incidence, etiology and prognosis of CAP are insufficiently investigated.We conducted a population-based cohort study within a statutory health insurance in Germany from 2015 to 2018. CAP was retrieved by ICD-10-GM codes. Episodes of immunosuppression were identified by coded conditions (hematologic neoplasms, stem cell or organ transplantation, neutropenia, HIV, primary immunosuppressive syndromes) or treatments (immunosuppressants, antineoplastic drugs, systemic steroids). Endpoints were defined as occurrence of CAP (primary), hospitalization, 30-day mortality and CAP associated with rare pathogens. Our analysis utilized the Andersen-Gill model adjusted for sex, age, level of long-term care, vaccination status, community type and comorbidities.942,008 individuals with 54,781 CAPs were included (hospitalization 55%, 30-day mortality 14.5%). 6% of individuals showed at least one episode of immunosuppression during the study period with systemic steroids (39.8%) and hematologic neoplasms (26.7%) being most common. Immunosuppression was recorded in 7.7% of CAPs. Besides classical risk factors such as age and level of long-term care, immunosuppressed patients were most prone to CAP (HR 2.4[2.3-2.5]) and consecutive death (HR 1.9[1.8-2.1]). Organ and stem cell transplantation (HR 3.2[2.6-4.0] and 2.8[2.1-3.7], respectively), HIV (HR 3.2[1.9-5.4]) and systemic steroids (> 20 mg prednisone daily dose equivalent (HR 2.7[2.4-3.1])) showed the highest risk for contracting CAP. CAP by rare pathogens was strongly associated with immunosuppression (HR 17.1[12.0-24.5]), especially HIV (HR 34.1[7.6-153]) and systemic steroids (HR 8.2[4.6-14.8]).Our study elucidates the relevance of particular immunosuppressive conditions including systemic steroids for occurrence and prognosis of CAP.