Outcomes of immunocompromised adults hospitalized with laboratory-confirmed influenza in the United States, 2011-2015.

BACKGROUND: Hospitalized immunocompromised (IC) adults with influenza may have worse outcomes than hospitalized non-immunocompromised adults.

METHODS: We identified adults (≥18 years) hospitalized with laboratory-confirmed influenza during 2011-2015 seasons through CDC's Influenza Hospitalization Surveillance Network. IC patients had ≥1: HIV/AIDS, cancer, stem cell or organ transplantation, non-steroid immunosuppressive therapy, immunoglobulin deficiency, asplenia, or other rare conditions. We compared demographic and clinical characteristics of IC and non-IC adults using descriptive statistics and used multivariable logistic regression and Cox proportional hazards models to control for confounding by patient demographic characteristics, pre-existing medical conditions, influenza vaccination, and other factors.

RESULTS: Among 35,348 adults, 3633 (10%) were IC; cancer (44%), non-steroid immunosuppressive therapy (44%), and HIV (17%) were most common. IC patients were more likely than non-IC patients to have received influenza vaccination (53% vs. 46%; p<0.001), and ~85% of both groups received antivirals. In multivariable analysis, IC adults had higher mortality (adjusted odds ratio (aOR) [95% confidence interval (CI)]: 1.46 [1.20-1.76]). Intensive care was more likely among IC patients 65-79 years (aOR [95% CI]: 1.25 [1.06-1.48]) and >80 years (aOR [95% CI]: 1.35 [1.06-1.73]) compared with non-IC patients in those age groups. IC patients were hospitalized longer (adjusted hazard ratio of discharge [95% CI]: 0.86 [0.83-0.88]) and were more likely to require mechanical ventilation (aOR [95% CI] 1.19 [1.05-1.36]).

CONCLUSIONS: Substantial morbidity and mortality occurred among IC adults hospitalized with influenza. Influenza vaccination and antiviral administration could be increased in both IC and non-IC adults.