Title : Community-acquired pneumonia in immunocompromised adults: A narrative review of the literature

Introduction/Aim: Community-acquired pneumonia (CAP) remains a major cause of morbidity and mortality. The aim of this narrative review is to evaluate the prognostic impact of the immunocompromised state in adults with CAP, focusing on mortality, clinical severity and microbiological etiology.

Methodology: An extended literature search for English-language studies of the last decade (2015-2025) was conducted. Due to the high clinical and methodological heterogeneity of the included studies, a quantitative meta-analysis was not performed. Instead, data regarding clinical outcomes and microbiological profiles were synthesized and analyzed utilizing a descriptive, narrative synthesis framework.

Results: The descriptive synthesis of the available data reveals that, despite presenting at a significantly younger age (age paradox), immunocompromised patients face a more than two-fold independent risk of mortality compared to immunocompetent controls (adjusted OR: 2.30). They also exhibit higher rates of clinical deterioration and intensive care unit (ICU) admission, with a median LOS ranging from 3.9 to 12 days. Crucially, a radical shift in the microbiological landscape was identified: a 17.1-fold increased risk for opportunistic pathogens, alongside a high prevalence of Gram-negative bacteria and polymicrobial (viral/fungal) co-infections. This etiological shift creates a critical 30% "coverage gap" in current standard empiric antibiotic guidelines.

Conclusions: The immunocompromised state acts as an independent and prognostic marker of mortality in CAP. There is an urgent need to update clinical guidelines by incorporating "augmented" risk stratification systems, specialized therapeutic algorithms, and promoting targeted vaccination strategies.

Dr. Elli Kouriannidi is a medical doctor training in internal medicine with a dedicated focus on specializing in infectious diseases. She is currently completing her Master's degree in Public Health at the University of West Attica. Dr. Kouriannidi’s research and clinical interests include global pandemic preparedness, public health policy, and the execution of clinical trials, having actively contributed to clinical research at a medical institute. She is an active young scientist member of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) and is committed to advancing infectious disease management and surveillance.