Vaccination programs for older adults in an era of demographic change

Abstract

Objectives: Populations are aging worldwide. This paper summarizes some of the challenges and opportunities due to the increasing burden of infectious diseases in an aging population.

Results: Older adults typically suffer elevated morbidity from infectious disease, leading to increased demand for healthcare resources and higher healthcare costs. Preventive medicine, including vaccination can potentially play a major role in preserving the health and independence of older adults. However, this potential of widespread vaccination is rarely realized. Here, we give a brief overview of the problem, discuss concrete obstacles and the potential for expanded vaccination programs to promote healthy aging.

Conclusion: The increasing healthcare burden of infectious diseases expected in aging populations could, to a large extent, be reduced by achieving higher vaccination coverage among older adults. Vaccination can thus contribute to healthy aging, alongside healthy diet and physical exercise. The available evidence indicates that dedicated programs can achieve substantial improvements in vaccination coverage among older adults, but more research is required to assess the generalizability of the results achieved by specific interventions (see Additional file 1).

Keywords: Demographic change; Healthy aging; Vaccination programs; Vaccines.

Fig. 1

Healthy vs premature aging. Typically, aging is associated with a decline in physical capability, during adulthood, from being fit and physically active to being well (that is, without obvious physical incapacity, but with reduced physical activity). In most adults, the later phases of life are characterized by frailty and disability. Disability is simply enough defined as the inability to perform basic day-to-day functions without assistance. Frailty is more difficult to define, but is often identified as meeting 3 or more of the following clinical criteria: a low level of physical activity, exhaustion or low energy, muscle weakness, slowness, and unintentional weight loss. The underlying etiology of frailty is poorly understood, but includes comorbidities such as diabetes, obesity and respiratory illnesses. Immune dysfunction also seems to be a key factor in two ways. First, through chronic inflammation, mitochondrial dysfunction and cellular senescence that may degrade the endocrine, hematologic and musculoskeletal systems, and secondly, by increasing susceptibility to infections, which can further harm these physiologic systems. The ideal of healthy aging (living with as little time spent in frailty or disability) is contrasted to rapid aging in this simple schematic. In reality, however, aging for most people is a nonlinear process. Acute incidents such as physical trauma from falls, social stressors such as divorce or death of a spouse, or acute illness (for example, from cardiac disease or infection) can trigger sudden losses of capacity, which in older individuals, become increasingly difficult to recover from. This places a priority on intervention to prevent those acute incidents to prevent frailty/disability and maintain quality of life

Fig. 2

Components of successful vaccination programs. Healthcare systems are more than just government and business infrastructure: they comprise everyone involved in the process—politicians, healthcare providers and the general public. Each part of the polity engages in dialogue with the other parts, and it is plain that for the establishment of successful vaccination programs—whether in children or in adults—all parts must be in general agreement [88, 89]. In addition, each part of the polity has specific roles in terms of delivery, dialogue and acceptance, as indicated by the labeled arrows. The media plays a significant, but different role. While not (in theory) directly involved in the process, it is the channel through which much of the dialogue is conducted, and can also act as an “amplifier”—for example, increasing the visibility and impact of public concerns or hesitancy, or alternatively promoting vaccination by reporting on disease-related deaths or vaccine benefits