Efficacy of Influenza Vaccination among Chronic Ill Patients :Retrospective Case Control Study

Abstract

Background Influenza is one of the preventable respiratory disease by annual vaccination. Elderly people and patients with chronic medical disease are the primary target for influenza vaccination according to ACIP (Advisory Committee on Immunization). This study was done to determine whether influenza vaccination affects hospitalization due to influenza like illness or it's related complications among chronic ill patients.

Materials and methods Retrospective, case-control study was conducted for 5 months (Nov. 1999-Mar. 2000). Physicians from two-university hospitals in Korea were instructed to collect clinical data, sera from subjects presenting with a flu-like illness or flu-related exacerbation in patients with chronic underlying diseases. We compared the vaccination history of case patients with control. Logistic regression analysis was used to calculate the odd ratio and efficacy of influenza vaccination.

Results Hospitalization due to ILI (influenza like illness) or it's related complications were observed more frequently in patients with chronic lung disease (25.3%) and chronic cardiac disease (31.3%) compared to others. Influenza vaccination resulted in fewer hospitalization with ILI or ILI-related acute exacerbation of underlying disease in chronic ill patients (adjusted odd ratio, 0.328 [CI, 0.14 to 0.73]) during influenza seasons.

Conclusion For patients with chronic disease, influenza vaccination is associated with substantial health benefit including fewer hospitalization. Health care providers should take advantage of all opportunities to immunize these high-risk patients.