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BackgroundRates of influenza hospitalizations differ by age, but few data are available regarding differences in laboratory-confirmed rates among adults aged ≥65 years.MethodsWe evaluated age-related differences in influenza-associated hospitalization rates, clinical presentation, and outcomes among 19 760 older adults with laboratory-confirmed influenza at 14 FluSurv-NET sites during the 2011–2012 through 2014–2015 influenza seasons using 10-year age groups.ResultsThere were large stepwise increases in the population rates of influenza hospitalization with each 10-year increase in age. Rates ranged from 101–417, 209–1264, and 562–2651 per 100 000 persons over 4 influenza seasons in patients aged 65–74 years, 75–84 years, and ≥85 years, respectively. Hospitalization rates among adults aged 75–84 years and ≥85 years were 1.4–3.0 and 2.2–6.4 times greater, respectively, than rates for adults aged 65–74 years. Among patients hospitalized with laboratory-confirmed influenza, there were age-related differences in demographics, medical histories, and symptoms and signs at presentation. Compared to hospitalized patients aged 65–74 years, patients aged ≥85 years had higher odds of pneumonia (aOR, 1.2; 95% CI, 1.0–1.3; P = .01) and in-hospital death or transfer to hospice (aOR, 2.1; 95% CI, 1.7–2.6; P < .01).ConclusionsAge-related differences in the incidence and severity of influenza hospitalizations among adults aged ≥65 years can inform prevention and treatment efforts, and data should be analyzed and reported using additional age strata.

Background Influenza virus infection most commonly causes acute respiratory tract illness, however may also lead to non-respiratory complications including acute cardiovascular (CV) events. We describe the frequency of and risk factors for acute CV events in adults hospitalized with influenza in the United States. Methods We included adults aged > 18 years hospitalized during influenza seasons 2010–2011 through 2017–2018 in FluSurv-NET, a multi-state population-based surveillance system that includes detailed medical chart review of patients hospitalized with laboratory-confirmed influenza. We defined acute CV events by International Classification of Diseases (ICD) primary and secondary discharge diagnosis codes for acute heart failure (aHF), acute ischemic heart disease (aIHD), hypertensive crisis, cardiogenic shock, acute myocarditis, acute pericarditis and cardiac tamponade. We calculated the frequency of acute CV events and used multivariable logistic regression among the 87% treated with influenza antivirals to identify independent factors associated with aHF and aIHD, the two most common diagnoses. Results Of 80,374 adults hospitalized with laboratory-confirmed influenza, 12% had > 1 acute CV event. We found that aHF (46%) and aIHD (42%) were the most common, followed by hypertensive crisis (8%), cardiogenic shock (3%), acute myocarditis (0.7%), acute pericarditis (0.4%) and cardiac tamponade (0.2%). Compared with treated patients without an acute cardiovascular event, treated patients with aHF (Figure A) and aIHD (Figure B) were more likely to be older, currently/formerly use tobacco and have underlying conditions including cardiovascular disease, diabetes mellitus, and kidney disease. Conclusion Among adults hospitalized with laboratory-confirmed influenza, acute CV events are common, particularly among those with prior cardiovascular disease. During the influenza season, clinicians should consider influenza virus infection in hospitalized adults who present with acute CV events. Non-respiratory complications, specifically aHF and aIHD, may be an under-recognized contributor to the burden of influenza. Disclosures All authors: No reported disclosures.

Background Few data describe the epidemiology of influenza among adults ≥65 years old according to age strata. We evaluated age-related differences in influenza-associated hospitalization rates, clinical presentation, and outcomes among older adults at 14 FluSurv-NET sites during the 2011–2012 through 2014-2015 influenza seasons. Methods Study patients were hospitalized ≤14 days after and ≤3 days before a positive influenza test. Age strata were 65–74, 75–84, and ≥85 years old. We adjusted hospitalization rates for under detection and assessed for age-related trends in risk factors and symptoms. We used logistic regression to calculate odds ratios (OR) for pneumonia and in-hospital death adjusted for season, sex, nursing home residence, smoking, medical comorbidities, influenza vaccination, and study site. Results There were 19,760 patients, including 5,956 aged 65–74 years, 6,998 aged 75–84 years, and 6,806 aged ≥85 years. There was a stepwise increase in hospitalization rates with age (figure). Increasing age was positively associated with female sex, nursing home residence, neurologic disorder, cardiovascular and renal disease, and vaccination, and inversely associated with morbid obesity, smoking, asthma, chronic metabolic disease, and immunosuppression (P < 0.01). Among 10,548 (53.3%) patients with symptom data from 2014 to 2015, increasing age was associated with a higher prevalence of altered mental status and lower prevalence of fever, myalgias, respiratory or gastrointestinal symptoms, and headache (P ≤ 0.01). Compared with 65–74 year olds, older patients had a higher risk of pneumonia (≥85 year-olds: OR 1.2, 95% CI 1.0, 1.3, P = 0.01) and death (75–84 year olds: OR 1.4, 95% CI 1.2, 1.7, P < 0.01; ≥85 year-olds: OR 2.1, 95% CI 1.7, 2.6, P < 0.01). Conclusion There are age-related differences in the epidemiology, clinical presentation, and outcomes of older adults hospitalized with influenza. These may reflect differences in health status and healthcare provider practice patterns. Public health epidemiologists should consider using additional age strata in ≥65 year-olds when analyzing influenza surveillance data. Clinicians should be aware that influenza among the oldest adults may present atypically and that mortality is increased. Disclosures E. J. Anderson, NovaVax: Grant Investigator, Research grant. Pfizer: Grant Investigator, Research grant. AbbVie: Consultant, Consulting fee. MedImmune: Investigator, Research support. PaxVax: Investigator, Research support. Micron: Investigator, Research support. W. Schaffner, Merck: Member, Data Safety Monitoring Board, Consulting fee. Pfizer: Member, Data Safety Monitoring Board, Consulting fee. Dynavax: Consultant, Consulting fee. Seqirus: Consultant, Consulting fee. SutroVax: Consultant, Consulting fee. Shionogi: Consultant, Consulting fee.