Adult vaccination is inversely associated with incident Alzheimer’s Disease and Related Dementias.

We determined if Tetanus, Diphtheria and Pertussis (Tdap) vaccination was linked to incident Alzheimer’s Disease and dementia among adults with Down Syndrome, 50% of whom develop Alzheimer’s Disease by age 60.

This is a retrospective cohort study using TriNetX nationally distributed electronic health records from 2013 to 2024.

Historical medical record data.

5,591 patients with Down Syndrome across the United States. Eligible patients were free of Alzheimer’s Disease and dementia prior to index. Index date could occur 1/1/2015 to 1/1/2020 allowing for 5 to 10 years of possible follow-up time.

Vaccination was measured using product name and procedure codes and Alzheimer’s Disease and dementias was defined by ICD-10 codes.

The mean age of the cohort was 50.0 (±8.3), 50.1% were female and 72.1% were White. After controlling for confounding, Tdap vaccination vs. remaining without Tdap vaccination was associated with lower Alzheimer’s Disease and dementia risk (HR=0.74; 95%CI:0.57-0.98).

In a cohort of patients with Down Syndrome, Tdap vaccination was associated with a 26% lower risk for Alzheimer’s Disease and dementia. This is a novel and important finding because existing studies of vaccination and reduced risk for Alzheimer’s Disease and dementia have been among cognitively intact adults. This study reveals benefits of vaccination even among those at high risk for Alzheimer’s Disease and dementia due to Down Syndrome. Future studies are needed to understand the mechanisms underlying this relationship.