1613. Rates of Hospitalization for Community-Acquired Pneumonia Among US Adults: A Systematic Review

Background Community-acquired pneumonia (CAP) develops in persons outside of a healthcare facility and is associated with significant morbidity and mortality. Estimating the incidence of CAP is challenging because it lacks a standardized case definition and because study designs and selection criteria vary. Reconciling these differences across studies is critical for understanding the true burden of CAP which, in turn, informs prevention strategies, including vaccination. Methods We performed a systemic literature review of studies describing the incidence of hospitalized CAP among adults in the United States. Specifically, we examined the impact of the following study characteristics on estimates of incidence: (i) study population, (ii) study type and data source, and (iii) diagnostic criteria for pneumonia. Results After review of 8361 articles as of January 31, 2019, we identified 26 studies which contained 39 unique CAP estimates. Among adults ≥65 years of age, annual rates of hospitalized CAP ranged from 847 to 3,500 per 100,000 persons with median = 1,830. Rates were lower in studies that excluded patients with healthcare-associated (but community-onset) pneumonia (HCAP; median = 2,003 vs. 1,286; P = .02) or immunocompromising conditions (median = 1,895 vs. 1,409; P = .29). Rates of CAP were also lower in studies that used more restrictive criteria for diagnosing pneumonia (e.g., pneumonia coded in any diagnosis position [median = 2,246] vs. pneumonia coded in the first position only [median = 1,375] in studies of administrative claims; P = 0.03). For adults <65 years of age, annual rates of CAP were lower (range = 89 to 1,024 per 100,000; median = 210). Conclusion CAP causes a significant disease burden among adults, particularly among those ≥65 years of age where the incidence of hospitalization is approximately 2,000 per 100,000 annually. Commonly-applied exclusion criteria (e.g., persons with HCAP or immunocompromising conditions) or restrictive case definitions (e.g., only including pneumonias coded in the primary diagnosis position) have led to systematic underestimation of CAP incidence in many previous studies. Understanding the true burden of adult CAP is critical for highlighting the ongoing need for expanded prevention programs, including vaccination. Disclosures All authors: No reported disclosures.