Association of Chronic Medical Conditions With Severe Outcomes Among Nonpregnant Adults 18–49 Years Old Hospitalized With Influenza, FluSurv-NET, 2011–2019

Abstract

Abstract Background Older age and chronic conditions are associated with severe influenza outcomes; however, data are only comprehensively available for adults ≥65 years old. Using data from the Influenza Hospitalization Surveillance Network (FluSurv-NET), we identified characteristics associated with severe outcomes in adults 18–49 years old hospitalized with influenza. Methods We included FluSurv-NET data from nonpregnant adults 18–49 years old hospitalized with laboratory-confirmed influenza during the 2011–2012 through 2018–2019 seasons. We used bivariate and multivariable logistic regression to determine associations between select characteristics and severe outcomes including intensive care unit (ICU) admission, invasive mechanical ventilation (IMV), and in-hospital death. Results A total of 16 140 patients aged 18–49 years and hospitalized with influenza were included in the analysis; the median age was 39 years, and 26% received current-season influenza vaccine before hospitalization. Obesity, asthma, and diabetes mellitus were the most common chronic conditions. Conditions associated with a significantly increased risk of severe outcomes included age group 30–39 or 40–49 years (IMV, age group 30–39 years: adjusted odds ratio [aOR], 1.25; IMV, age group 40–49 years: aOR, 1.36; death, age group 30–39 years: aOR, 1.28; death, age group 40–49 years: aOR, 1.69), being unvaccinated (ICU: aOR, 1.18; IMV: aOR, 1.25; death: aOR, 1.48), and having chronic conditions including extreme obesity and chronic lung, cardiovascular, metabolic, neurologic, or liver diseases (ICU: range aOR, 1.22–1.56; IMV: range aOR, 1.17–1.54; death: range aOR, 1.43–2.36). Conclusions To reduce the morbidity and mortality associated with influenza among adults aged 18–49 years, health care providers should strongly encourage receipt of annual influenza vaccine and lifestyle/behavioral modifications, particularly among those with chronic medical conditions.