The aging process in humans is associated with a decrease in immune function (immunosenescence) and an increase in comorbid disorders. When combined with environmental factors this can lead to an increased risk and severity of infectious diseases. Diseases in older adults (>/=70 years) tend to be more severe and have a greater impact on health outcomes such as morbidity, disability, quality of life and mortality. However, some of the more common infections such as influenza and pneumococcal infection are vaccine preventable, but the uptake of such preventive strategies in adults has been poor. In this review some of the key clinical findings supporting the benefits of adult immunization are highlighted. Vaccination of the adult population needs to be a key component of a healthy aging strategy, since there is already convincing evidence that this approach can have an important impact on morbidity, mortality and quality of life.