ImmunologyTier 2Medical Sciences concept

Immunosenescence - mechanism of reduced vaccine response in elderly

Core concept

Immunosenescence - progressive decline in immune function with age, affecting both innate and adaptive arms
Thymic involution -> fewer naive T cells, shrinking T cell receptor repertoire, clonal expansion of memory/exhausted T cells
Reduced B cell diversity and germinal centre response -> lower-affinity, shorter-lived antibody responses to new antigens

Key detail

"Inflammaging" - chronic low-grade inflammation (raised IL-6, TNF-alpha) accompanies immunosenescence and itself blunts vaccine response
Result: lower seroconversion rates and faster antibody waning after standard-dose vaccines in older adults
Response to novel antigens is more impaired than recall responses to previously encountered antigens (the memory pool is relatively preserved)

Clinical relevance

Rationale for high-dose and adjuvanted influenza vaccines in patients aged >=65y - compensating for the blunted response to standard dose
Rationale for age-targeted recombinant zoster and pneumococcal vaccination strategies
Explains higher morbidity/mortality from vaccine-preventable illness in older adults despite vaccination - protection is partial, not absent

Correlations

Influenza and pneumococcal vaccination schedules
Frailty and immune function
Vaccine response in immunosuppression (contrasting mechanism)

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