Lay summary
Emerging research suggests that certain infections and immune responses may contribute to the development of dementia. In the absence of a cure, reducing incidence and delaying onset is a public‑health priority. We will assess whether AS01‑adjuvanted vaccines, recommended for older adults’ recombinant zoster vaccine, and the respiratory syncytial virus (RSV) vaccine lower dementia risk compared with non‑adjuvanted alternatives (Zostavax® and Influvac Tetra). AS01‑adjuvanted immunisation may confer brain‑protective effects beyond infection prevention by modulating innate immunity. Our study will generate real‑world evidence on off‑target benefits, focusing on groups underrepresented in trials, including older adults, Māori and Pasifika, and immunocompromised people. By informing policy and practice, this evidence can support the incorporation of adult immunisation into dementia‑prevention frameworks, enabling equitable, high‑coverage interventions that reduce acute‑care use and enhance quality of life for whānau across Aotearoa.