Vaccines for the elderly

Abstract

Vaccination is the most efficient strategy to prevent infectious disease. The increased vulnerability to infection of the elderly makes them a particularly important target population for vaccination. However, most vaccines are less immunogenic and efficient in the elderly because of age-related changes in the immune system. Vaccination against influenza, Streptococcus pneumoniae and varicella zoster virus is recommended for the elderly in many countries. Various strategies such as the use of adjuvants and novel administration routes are pursued to improve influenza vaccination for the elderly and recent developments in the field of pneumococcal vaccination led to the licensure of protein-conjugated polysaccharide vaccines containing up to 13 serotypes. As antibody titres are generally lower in the elderly and-particularly for inactivated vaccines-decline fast in the elderly, regular booster immunizations, for example against tetanus, diphtheria and, in endemic areas, tick-borne encephalitis, are essential during adulthood to ensure protection of the elderly. With increasing health and travel opportunities in old age the importance of travel vaccines for persons over the age of 60 is growing. However, little is known about immunogenicity and efficacy of travel vaccines in this age group. Despite major advances in the field of vaccinology over the last decades, there are still possibilities for improvement concerning vaccines for the elderly. Novel approaches, such as viral vectors for antigen delivery, DNA-based vaccines and innovative adjuvants, particularly toll-like receptor agonists, will help to achieve optimal protection against infectious diseases in old age.

Low Thymic Activity and Dendritic Cell Numbers Are Associated with the Immune Response to Primary Viral Infection in Elderly Humans

“…Underlying mechanisms of immunological aging are mostly studied in animal models (4,5), but the direct translation of these results to humans is complicated by the much higher life expectancy and individual systemic immune properties (6,7). Further knowledge about the aged immune system has been obtained by comparing young and aged immune systems in the steady-state (8) or after secondary, booster vaccinations, such as tetanus or influenza (9,10). However, the human immune response to an entire primary acute infection, from inoculation to complete resolution, has not been analyzed in elderly people in detail until now.…”

Elderly vaccination—The glass is half full

“…Whilst improved vaccine technologies must be developed to address the weakened elderly immune system, improving vaccination coverage and recording of adult vaccinations, addressing provider and patient barriers, and building an evidence-base of vaccine RCTS in the frail elderly are equally important. Other neglected areas include travel vaccination in the elderly, with a higher proportion of the elderly travelling after retirement [25]. Finally, cancerpreventing vaccines such as hepatitis B and Human papillomavirus vaccines have a long lead time from vaccination in childhood to prevention of cancer [46], and their benefits in adulthood are heavily discounted in standard cost-effectiveness analyses, which are biased against long-term benefits of vaccines [47].…”

“…Reduced numbers and defects in antigen-presenting cells such as plasmacytoid dendritic cells have been described; altered activation of T cells, especially CD8 cells, results in impaired cytokine production and cell mediated immunity; defects in humoral immunity have also been described, with reduced function and diversity of B cells [25,26]. The exponential rise of herpes zoster incidence after the age of 50, as first described by Hope-Simpson, is thought to reflect the corresponding decline in cell-mediated immunity, with the elderly being at risk for herpes zoster despite commonly having high antibody levels to varicella-zoster virus [27,28].…”

“…Adjuvants have been explored as a means of improving influenza vaccine responses in the elderly [25], as has intradermal administration [41]. Both show some promise.…”

“…The exponential rise of herpes zoster incidence after the age of 50, as first described by Hope-Simpson, is thought to reflect the corresponding decline in cell-mediated immunity, with the elderly being at risk for herpes zoster despite commonly having high antibody levels to varicella-zoster virus [27,28]. Immunosenescence combined with the tendency for waning vaccine-induced immunity for many vaccines of importance to the elderly, such as influenza, pneumococcus and herpes zoster [6,25,29], places the elderly at greater risk and poses a challenge that require innovative solutions.…”