Effects of Annual Influenza Vaccination on Winter Mortality in Elderly People With Chronic Heart Disease

Cinta de Diego; Angel Vila-Córcoles; Olga Ochoa; Teresa Rodriguez-Blanco; Elisabeth Salsench; Imma Hospital; Ferran Bejarano; M. del Puy Muniain; Mercé Fortin; Montserrat Canals and EPIVAC Study Group

Disclosures

Eur Heart J. 2009;30(2):209-216. 

In This Article

Abstract and Introduction

Abstract

Aims: Although there is general agreement for the recommendation of the influenza vaccine to elderly and high-risk adults, the magnitude of clinical effectiveness and benefit from the annual vaccination is controversial. In this study, we have assessed the effects of annual influenza vaccination on winter mortality in older adults with chronic heart disease.
Methods and Results: Cohort study that included 1340 Spanish community-dwelling individuals 65 years or older who had chronic heart disease (congestive heart failure or coronary artery disease) followed from January 2002 to April 2005. Annual influenza vaccine status was a time-varying condition and primary outcome was all-cause death during the study period. Multivariable Cox proportional-hazard models adjusted by age, sex, and comorbidity were used to evaluate vaccine effectiveness. Influenza vaccination was associated with a significant reduction of 37% in the adjusted risk of winter mortality during the overall period 2002–2005. The attributable mortality risk reduction in vaccinated people was 8.2 deaths per 1000 person-winters. We estimated that one death was prevented for every 122 annual vaccinations (ranging between 49 in Winter 2005 and 455 in Winter 2003).
Conclusion: Our results suggest a benefit from the influenza vaccination and support an annual vaccination strategy for elderly people with cardiac diseases.

Introduction

Influenza viruses are a major determinant of morbidity and mortality mainly caused by respiratory disease. The incidence of flu is higher in children and younger adults than in older individuals, but influenza-associated morbidity and mortality increase with age, especially for individuals with underlying medical conditions such as chronic heart diseases.[1–3]

During influenza epidemics, it has been reported that this viral infection was associated with increased death rates from cardiovascular diseases and a rise in autopsy-confirmed coronary deaths.[4] Clinical and experimental data suggest that autoimmune mechanisms are responsible for accelerated coronary atherosclerosis in influenza infection. Both cellular and humoral autoimmune modes could participate in the onset or progression of atherosclerotic lesions due to influenza infection.[5,6]

To date, although some studies have reported that influenza infection causes excess specific cardiac mortality,[4,7] the effect of the influenza vaccination in preventing mortality among patients with chronic heart diseases is not well known. This is because few studies have specifically focused on these patients[8–10] and their conclusions were not always in favour of vaccination.[10]

On the other hand, although the effectiveness of the influenza vaccination in preventing mortality has been extensively studied among hospitalized or institutionalized patients during severe influenza seasons, few large studies have systematically evaluated the clinical benefit of vaccination in community-dwelling individuals over the medium or long term,[11–15] and little is known about the effectiveness of the annual vaccination programmes in high-risk elderly people living in the community.

To assess influenza vaccine effectiveness in preventing mortality, we conducted a cohort study of 11 240 Spanish community-dwelling elderly individuals followed between 2002 and 2005. The analysis on vaccine effectiveness covering the general elderly and chronic obstructive pulmonary disease patients has been published.[15,16] In the present study, we assessed the relationship between the annual influenza vaccine status and all-cause winter mortality among a group of 1340 individuals with chronic heart disease.

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