Influenza vaccination and risk of dementia: a systematic review and meta-analysis

Abstract

Background: The association between influenza vaccination and a reduction in dementia was unclear with inconsistent evidence. We aimed to evaluate the association between influenza vaccination and dementia risk in the overall population and the high-risk populations for dementia, such as patients with chronic kidney syndrome (CKD), chronic obstruction pulmonary disease (COPD) and vascular disease.

Methods: We performed a systematic review and searched PubMed, Embase and CENTRAL from inception to 6 April 2025. The risk of bias was assessed using the Newcastle-Ottawa Scale. A random-effects model meta-analysis was executed.

Results: We included eight cohort studies with 9,938,696 subjects. Except for one study, the risk of bias of all other included studies was low. Influenza vaccination was associated with a reduced risk of incident dementia in high-risk populations for dementia, but not in the overall population (HR 0.93; 95% CI: 0.86-1.01). For high-risk populations, more than one dose of influenza vaccination showed an association with a lower risk of incident dementia (2-3 doses: HR 0.84; 95% CI: 0.76-0.92; ≥ 4 doses: HR 0.43; 95% CI: 0.38-0.48).

Conclusion: Influenza vaccination was associated with a decreasing risk of incident dementia in a dose-response manner.

Keywords: Alzheimer disease; aged; dementia; influenza vaccination; meta-analysis; older people; systematic review.