# Shingles Vaccination and Dementia Prevention

Shingles vaccination has promising local causal evidence for preventing or delaying dementia diagnoses; product-wide efficacy, causal magnitude and the mediator remain unsettled.

The preregistered primary-subclaim rule returns Δ from SC2: the strongest evidence is a positive local age-eligibility natural experiment for live-zoster vaccination and recorded dementia, with international eligibility corroboration. Multiple related discontinuity analyses do not automatically supply independently failing causal modalities. Receipt-effect assumptions, a quantitative2026 critique, diagnosis ascertainment, product transfer and exploratory sex boundaries prevent a higher grade. Weakest-link returns Β; primary and scope-matched return Δ. This is stronger than an ordinary association but remains a bounded causal-inference judgment rather than completed randomized dementia-prevention proof.

Country replication supports local eligibility effects; age-near-cutoff, live product, follow-up and recorded diagnosis remain explicit. Recombinant cohorts are supportive but generally observational. Canadian women-positive/men-nonsignificant with interactionP=.218 cannot define a proven sex beneficiary boundary.