Effect of influenza vaccination on the prognosis of hospitalized influenza patients

Abstract

Objectives: This study aimed to assess whether influenza vaccination reduces the risk of severe and fatal outcomes in influenza inpatients aged ≥65 years.

Methods: During the 2013-2014 influenza season persons aged ≥65 years hospitalized with laboratory-confirmed influenza were selected in 19 Spanish hospitals. A severe influenza case was defined as admission to the intensive care unit, death in hospital or within 30 days after admission. Logistic regression was used to compare the influenza vaccination status between severe and non-severe influenza inpatients.

Results: Of 433 influenza confirmed patients, 81 (19%) were severe cases. Vaccination reduced the risk of severe illness (odds ratio: 0.57; 95%CI: 0.33-0.98). The cumulative number of influenza vaccine doses received since the 2010-2011 season was associated with a lower risk of severe influenza (odds ratio: 0.78; 95% CI 0.66-0.91).

Conclusion: Adherence to seasonal influenza vaccination in the elderly may reduce the risk of severe influenza outcomes.

Keywords: Influenza virus; mortality; seasonal influenza vaccine; severe influenza; vaccine effectiveness.