Aging and impaired immunity to influenza viruses: implications for vaccine development.

Influenza infections are responsible for significant morbidity and mortality each year, with the highest infection rates found in the elderly population. The main strategy to reduce the impact of influenza infections in the elderly population is vaccination. However, the efficacy of influenza vaccines that are licensed for use in the elderly is relatively low (17-53%). The complex age-related changes that occur in both innate and adaptive immunity are thought to hamper the immune response to influenza immunization and to reduce protection against infection in the elderly. For the development of improved vaccines that overcome the limitations of an aged immune system, it is crucial to understand the mechanisms that lead to immune dysfunction. Here, we review the recent progress in unravelling the mechanisms behind the age-related immune dysfunction in elderly, as well as the recent developments in improving influenza vaccines and identification of new correlates of protection.