Clinical Features and Outcomes of Immunocompromised Adults Hospitalized with Laboratory-confirmed Influenza in the USA, 2011–2015

Abstract

Background. Data on immunocompromised (IC) adults with influenza are limited but suggest they may present differently and have worse outcomes than non-IC adults. Using a national surveillance system, we describe the epidemiology of IC adults hospitalized with influenza. Methods. We analyzed data on adults (aged >=18 years) hospitalized with laboratory- confirmed influenza during the 2011-2012 through 2014-2015 seasons and reported to CDC's Influenza Hospitalization Surveillance Network (FluSurv-NET). We defined IC patients as having >=1 of the following: HIV, AIDS, cancer, stem cell or organ transplantation, non-steroid immunosuppressive therapy, immunoglobulin deficiency, asplenia, and other rare conditions. We compared IC and non-IC patients using chi2 or Fisher's exact tests and t-tests or Mann-Whitney U tests. Results. Among 35,348 adults hospitalized over four seasons, 3,633 (10%) were IC. The most common IC conditions were cancer (44%), non-steroid immunosuppressive therapy (44%), and HIV (17%). IC patients were younger than non-IC patients (mean 61 +/- 17 vs. 67 +/- 20 years; P < 0.01). IC patients were more likely to have underlying renal disease (27% vs. 18%) and liver disease (7% vs. 3%) and less likely to have most other chronic underlying conditions including obesity (18% vs. 23%), cardiovascular disease (40% vs. 47%), and chronic lung disease (35% vs. 41%; P < 0.01 for all). IC patients were more likely to have received influenza vaccination (53% vs. 46%; P < 0.01). Among cases with symptom data (2014-2015), IC patients were more likely to present with fever (68% vs. 61%; P < 0.01) but respiratory distress was similar (53% vs. 54%; P = 0.3). Overall, the majority of IC and non-IC patients received antivirals (87% vs. 85%; P < 0.01). IC patients had a longer duration of hospitalization (median (IQR) 4 (2-6) vs. 3 (2-6) days; P < 0.01) and were more likely to be diagnosed with pneumonia (34 vs. 31%; P < 0.01) and to require intensive care (18% vs. 16%; P = 0.01). Death during hospitalization occurred in 135 (3.7%) IC and 945 (3.0%) non-IC patients (P = 0.01). Conclusion. Among adults hospitalized with influenza, IC patients had worse outcomes including a longer duration of hospitalization and higher probability of pneumonia and intensive care unit admission, and increased all-cause mortality, although these results are not adjusted for potential confounders.