Overviewing Emerging Evidence of Vaccines, Dementia Risk, and Pathogen Protection: Pierre Tariot, MD

WATCH TIME: 6 minutes | Captions are auto-generated and may contain errors.

“It turns out that the more vaccines that you get, for any reason—polio, diphtheria, pertussis, herpes—the more there are unintended health consequences unrelated to the pathogen that’s been targeted. It looks like you’re less likely to get other infectious diseases, and in particular, for this meeting, it looks like, as a group, they tend to protect against subsequent onset of dementia."

Dementia is common among older adults and represents a major public health concern. Although prevention strategies are a priority, the potential role of vaccination in reducing dementia risk remains incompletely understood. In a recently published review, adult vaccinations, particularly against herpes zoster, influenza, pneumococcus, and tetanus-diphtheria–acellular pertussis, were associated with a lower risk of dementia.¹ Research on vaccinations and dementia risk was highlighted at the recently concluded 18th Clinical Trials on Alzheimer’s Disease (CTAD) Conference, held December 1-4, 2025, in San Diego, California.

At the meeting, one presentation described evidence from natural experiments supporting clinical trials of herpes zoster vaccination across populations without cognitive impairment, with mild cognitive impairment, and with established dementia.² Another presentation, a phase 2 study, reported that in adults with type 1 diabetes, multidose Bacille Calmette-Guérin (BCG) immunotherapy was associated with a statistically significant reduction in plasma p-tau217 over 5 years.³ Furthermore, a separate presentation showed that intradermal BCG vaccination induced transcriptional and metabolic reprogramming of central nervous system myeloid cells, consistent with trained immunity mechanisms relevant to neuroinflammation and AD pathology.⁴

At the 2025 CTAD Conference, Pierre Tariot, MD, director of Banner Alzheimer’s Institute, spoke with NeurologyLive^® to discuss an emerging area of interest focused on the broader, non–pathogen-specific effects of vaccines. He noted that data presented at the meeting included epidemiologic observations and translational findings suggesting potential associations between certain vaccinations and dementia-related outcomes. Tariot indicated that a few presentations also addressed population-level trends as well as underlying biological pathways and biomarker changes relevant to neurodegeneration, reflecting growing interest in immunologic strategies as a potential area for future investigation in AD and related disorders.

Click here to view more coverage of CTAD 2025.

REFERENCES
1. Maggi S, Fulöp T, De Vita E, Limongi F, Pizzol D, Di Gennaro F, Veronese N. Association between vaccinations and risk of dementia: a systematic review and meta-analysis. Age Ageing. 2025 Oct 30;54(11):afaf331. doi: 10.1093/ageing/afaf331. PMID: 41269248; PMCID: PMC12636520.
2. Xie M, Eyting M, Bommer C, et al. The Effect of Herpes Zoster Vaccination at Different Stages of the Dementia Disease Course: Implications for Defining the Study Population of Clinical Trials. Presented at: CTAD 2025; December 1-4; San Diego, CA. OC01.
3. Hashiguchi S, Hayashi H, Kartsounis N, et al. Impact of BCG Immunotherapy on Plasma P-tau217 in Patients With Type 1 Diabetes at Risk of Alzheimer’s Disease: A Five-Year, Phase II, Randomized, Controlled Trial. Presented at: CTAD 2025; December 1-4; San Diego, CA. LB29.
4. Arnold S, Kodali M, Li Z, et al. Impact of BCG Immunotherapy on Plasma P-tau217 in Patients With Type 1 Diabetes at Risk of Alzheimer’s Disease: A Five-Year, Phase II, Randomized, Controlled Trial. Presented at: CTAD 2025; December 1-4; San Diego, CA. P264.