%0 Journal Article
%T Influenza Vaccination in the Face of Immune Exhaustion: Is Herd Immunity Effective for Protecting the Elderly?
%A Pierre Olivier Lang
%A Dimitrios Samaras
%A Nikolaos Samaras
%A Sheila Govind
%A Richard Aspinall
%J Influenza Research and Treatment
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/419216
%X At the start of the 21st century, seasonal influenza virus infection is still a major public health concern across the world. The recent body of evidence confirms that trivalent inactivated influenza vaccines (TIVs) are not optimal within the population who account for approximately 90% of all influenza-related death: elderly and chronically ill individuals regardless of age. With the ever increasing aging of the world population and the recent fears of any pandemic influenza rife, great efforts and resources have been dedicated to developing more immunogenic vaccines and strategies for enhancing protection in these higher-risk groups. This paper describes the mechanisms that shape immune response at the extreme ages of life and how they have been taken into account to design more effective immunization strategies for these vulnerable populations. Furthermore, consideration will be given to how herd immunity may provide an effective strategy in preventing the burden of seasonal influenza infection within the aged population. 1. Introduction Infants and the elderly share a high vulnerability to infections and therefore have specific immunization requirement [1]. Foremost amongst vaccine infectious preventable diseases is influenza virus infection. Worldwide influenza causes 3¨C5 million of severe cases per year resulting in 250,000¨C350,000 deaths [2]. Indeed, while influenza affects people of all ages, young children and older adults, suffering or not from medical comorbid conditions, are particularly vulnerable. This results in increased morbidity and mortality [2¨C4]. While children have the highest rates of seasonal influenza infection and illness [3, 4], mortality in the elderly is just the tip of the iceberg in terms of disease burden. Influenza infection can also act within this population as a trigger for functional decline, decompensation of medical comorbid conditions, and/or cardiovascular and neurovascular acute diseases, being thus contributory to excessive hospitalization, antibiotic prescriptions, and a considerable economic burden [5¨C10]. Indeed, early immune protection initially relies on maternal antibodies, and this makes infants to become vulnerable to infections within a short time frame if failure of development of adaptive immunity in order to confer sustained protection [1, 11]. In those who approach the end of the normal life expectancy, the age-related decline in immune function, usually termed immunosenescence, partly explains the inability to resist influenza virus. Moreover, the elderly not only have problems in dealing with new
%U http://www.hindawi.com/journals/irt/2011/419216/