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Impact of Vaccination on Morbidity and Mortality in Adults Hospitalized With Influenza A, 2014–2015

Kaselitz, Timothy B. MD, MPH*; Martin, Emily T. PhD, MPH; Power, Laura E. MD, MPH†,‡; Cinti, Sandro MD‡,§

Infectious Diseases in Clinical Practice: November 2019 - Volume 27 - Issue 6 - p 328–333
doi: 10.1097/IPC.0000000000000777
Original Articles

Background Influenza A is a significant cause of in-hospital morbidity and mortality in the United States. While vaccination has proven the most effective means of preventing infection, data examining its impact on patients hospitalized with influenza A are lacking. This is particularly true during seasons when there is poor vaccine matching, such as the 2014–2015 season. We hypothesize that vaccination is associated with less in-hospital morbidity and mortality among adults hospitalized with influenza A in a large tertiary hospital during the 2014–2015 season.

Methods A retrospective chart review was conducted on all adults hospitalized with influenza A during the 2014–2015 season. Adjusting for confounders, multivariable logistic regression analyses were performed to examine the relationship between vaccination status and a variety of serious clinical outcomes.

Results Of 217 adults hospitalized with influenza A, 118 were vaccinated (54%). Serious outcomes were frequent; 14 patients (7%) died, 31 (14%) required intensive care unit admission, and 27 (12%) required mechanical ventilation. Adjusting for sociodemographic and clinical confounders, we show that vaccinated patients were significantly less likely to die (odds ratio [OR], 0.29; 95% confidence interval [CI], 0.09–0.99), require mechanical ventilation (OR, 0.35; 95% CI, 0.14–0.83), and suffer a severe outcome (intensive care unit admission or death) (OR, 0.41; 95% CI, 0.19–0.87).

Discussion Vaccination during the 2014–2015 season was associated with reduced morbidity and mortality among adults hospitalized with influenza A, despite the poor vaccine matching recognized during that season. Our findings suggest that during seasons with poor vaccine matching vaccination may afford protection against poor outcomes in patients hospitalized with influenza A.

From the *Department of Critical Care Medicine, University of Pittsburgh Medical Center, Pittsburgh, PA

Department of Epidemiology, University of Michigan School of Public Health

Division of Infectious Diseases, Department of Internal Medicine, University of Michigan Medical School

§Ann Arbor VA Medical Center, Ann Arbor, MI.

Correspondence to: Sandro Cinti, MD, Taubman Center, Floor 3 Reception D, 1500 E Medical Center Dr, SPC 5378, Ann Arbor, MI 48109. E-mail:

The authors have no funding or conflicts of interest to disclose.

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