Vaccination of Elderly People Affected by Chronic Diseases: A Challenge for Public Health

Elderly people have a limited regenerative capacity and are more susceptible to disease, syndromes, injuries, and illnesses than younger adults. There are many causes for this phenomenon, including anatomical and physiological changes and increased risk from hospitalization or invasive procedures, but most importantly, age-related changes in the functionality of the immune system, summarized as immunosenescence, also play a significant role. The immune system equally suffers from the effects of biological aging, exhibiting a progressive decline in function that collectively results in diminished humoral and cellular immune responses. In addition to alterations attributable to immunosenescence, other factors such as chronic disease, obesity, nutrition, frailty, functional status, or stress can affect immune function and further compromise the immune response to vaccination in older adults. The presence of one or two chronic diseases is associated with a 40- to 150-fold increase in the incidence rate of influenza or pneumonia. In addition, it is necessary to specify that other conditions (geriatric syndromes) make the elderly subject at greater risk for infection. Thus, these conditions contribute to increased susceptibility to infectious diseases in the elderly, some of which may be vaccine-preventable.