Association between vaccinations and risk of dementia: a systematic review and meta-analysis

Importance: Dementia is a highly prevalent issue in older people. Whilst the prevention of dementia is a public health priority, the role of vaccinations is still largely unexplored. Objective: The aim of this systematic review is to evaluate whether common adult vaccinations are associated with a reduced risk of dementia. Data sources: PubMed, Embase and Web of Science were searched from inception to 1 January 2025. Study selection: Observational studies comparing dementia and mild cognitive impairment incidence between vaccinated and unvaccinated adults aged ≥50 years. Data extraction and synthesis: Four reviewers independently extracted data and assessed study quality using the Newcastle-Ottawa Scale. Risk ratios (RRs) and 95% confidence intervals (CIs) were pooled using a random-effects model. Main outcomes and measures: Incidence of dementia, including its subtypes. Results: Twenty-one studies (n = 104 031 186 participants) were included. Vaccination against herpes zoster was associated with a reduced risk of any dementia (RR 0.76, 95% CI 0.69-0.83) and Alzheimer's disease (RR 0.53, 95% CI 0.44-0.64). Influenza vaccination was linked to a reduction in dementia risk (RR 0.87, 95% CI 0.77-0.99), as was pneumococcal vaccination (RR 0.64, 95% CI 0.47-0.87) for Alzheimer's disease. Tetanus, diphtheria, pertussis (Tdap) vaccination was also associated with a significant reduction for any dementia (RR 0.67, 95% CI 0.54-0.83). Conclusions and relevance: Adult vaccinations, particularly against herpes zoster, influenza, pneumococcus and Tdap, are associated with a lower risk of dementia. Vaccination strategies should be incorporated into public health initiatives for dementia prevention.