Abstract
Infectious diseases still represent a major challenge to human progress and survival. Especially elderly persons are more frequently and severely affected by infectious diseases and they display distinct features with respect to clinical presentation and treatment. Although vaccinations are considered a vital medical procedure for preventing morbidity and mortality caused by infectious diseases, the protective effect of vaccinations is abrogated in elderly persons. This is due to a decline in the functions of the immune system referred to as immunosenescence. The first part of this chapter will therefore summarize the status quo of the efficacy of vaccines in preventing morbidity and mortality caused by typical infectious diseases in the elderly, such as influenza, pneumonia and tuberculosis. The second part will then elucidate the underlying age-related mechanisms which may contribute to the decreased efficacy of vaccines. Based on the complex mechanisms involved in immunosenescence, strategies will be outlined which may be succesfful in enhancing protective immune responses following vaccination in elderly persons.