Vaccination in Older Adults and Elderly

Vaccination in older adults addresses the reality that ageing both raises the risk of severe infection and weakens the response to vaccines. Because the immune system changes with age, a process called immunosenescence, the field has developed enhanced strategies such as high-dose and adjuvanted vaccines to improve protection in this group against diseases including influenza, pneumococcal disease, and herpes zoster.

Definition

Vaccination in older adults is the tailoring of immunization to people of advanced age, who face higher infection-related morbidity and mortality and a diminished immune response, often addressed with enhanced (high-dose or adjuvanted) vaccine formulations.

Scope

The topic covers why older adults are a special population for vaccination, the immunological basis of reduced vaccine response with age, and the principal enhanced approaches and target diseases studied in this group. It is a reference overview of principles and evidence, not a list of recommended vaccines, ages, or doses for older adults.

Core questions

• How does ageing change the immune response to vaccines?
• Why do older adults bear a disproportionate burden of vaccine-preventable disease?
• How do high-dose and adjuvanted vaccines aim to overcome a weaker response?
• Which diseases are the main targets of vaccination in this group?

Key concepts

• Immunosenescence
• High-dose vaccines
• Adjuvanted vaccines
• Herpes zoster (shingles) prevention
• Influenza and pneumococcal disease in the elderly
• Vaccine effectiveness with age

Mechanisms

With age the immune system undergoes immunosenescence: thymic output declines, the repertoire of naïve T cells narrows, and antibody responses to new antigens weaken, so a standard vaccine often elicits lower and less durable protection than in younger adults. Two main strategies counter this. Increasing antigen dose, as in high-dose influenza vaccine, drives a stronger response; adding an adjuvant, as in the adjuvanted herpes zoster subunit vaccine, boosts and broadens the immune reaction, including the T-cell response relevant to controlling latent virus reactivation. These mechanistic adaptations are what distinguish vaccination strategy in older adults from that in younger populations.

Clinical relevance

Recognising that vaccines may work less well with age explains why enhanced formulations exist and why older adults are prioritised for several immunizations. This entry describes the principles and evidence for reference and education; the specific vaccines, formulations, and timing recommended for older adults are set by current guidelines and individual clinical assessment.

Epidemiology

Older adults experience the highest rates of severe outcomes from influenza and pneumococcal disease and a rising incidence of herpes zoster with age, making them a priority group for immunization. Trials and meta-analyses have quantified both the limits of standard vaccines and the gains from enhanced formulations in this population.

History

As populations aged, evidence accumulated that standard vaccines underperformed in the elderly, prompting the development and licensure of high-dose and adjuvanted influenza vaccines and, more recently, an adjuvanted subunit herpes zoster vaccine with high efficacy in older adults reported in 2015. These developments established enhanced immunization as a distinct strategy for ageing populations.

Debates

How much do enhanced vaccines improve real-world outcomes?

Enhanced formulations raise immunogenicity and, in trials, efficacy, but the magnitude of benefit on hard outcomes across diverse older populations and seasons remains an area of continued evaluation.

Key figures

• Carlos DiazGranados
• Anthony Cunningham
• Michael Osterholm

Seminal works

• diazgranados-2014
• lal-2015

Frequently asked questions

Why might a vaccine work less well in an older person?

Ageing weakens the immune system (immunosenescence), so the body often mounts a smaller and shorter-lasting response to a vaccine than it would in a younger adult.

What are high-dose and adjuvanted vaccines for?

They are designed to produce a stronger immune response in older adults, either by using more antigen or by adding a substance (adjuvant) that enhances the reaction, to compensate for a weaker baseline response.