The Impact of Routine Vaccinations on Alzheimer’s Disease Risk in Persons 65 Years and Older: A Claims-Based Cohort Study using Propensity Score Matching

BACKGROUND: Accumulating evidence suggests that adult vaccinations can reduce the risk of developing Alzheimer’s disease (AD) and Alzheimer’s disease related dementias. OBJECTIVE: To compare the risk for developing AD between adults with and without prior vaccination against tetanus and diphtheria, with or without pertussis (Tdap/Td); herpes zoster (HZ); or pneumococcus. METHODS: A retrospective cohort study was performed using Optum’s de-identified Clinformatics® Data Mart Database. Included patients were free of dementia during a 2-year look-back period and were≥65 years old by the start of the 8-year follow-up period. We compared two similar cohorts identified using propensity score matching (PSM), one vaccinated and another unvaccinated, with Tdap/Td, HZ, or pneumococcal vaccines. We calculated the relative risk (RR) and absolute risk reduction (ARR) for developing AD. RESULTS: For the Tdap/Td vaccine, 7.2% (n = 8,370) of vaccinated patients and 10.2% (n = 11,857) of unvaccinated patients developed AD during follow-up; the RR was 0.70 (95% CI, 0.68–0.72) and ARR was 0.03 (95% CI, 0.02–0.03). For the HZ vaccine, 8.1% (n = 16,106) of vaccinated patients and 10.7% (n = 21,417) of unvaccinated patients developed AD during follow-up; the RR was 0.75 (95% CI, 0.73–0.76) and ARR was 0.02 (95% CI, 0.02–0.02). For the pneumococcal vaccine, 7.92% (n = 20,583) of vaccinated patients and 10.9% (n = 28,558) of unvaccinated patients developed AD during follow-up; the RR was 0.73 (95% CI, 0.71–0.74) and ARR was 0.02 (95% CI, 0.02–0.03). CONCLUSION: Several vaccinations, including Tdap/Td, HZ, and pneumococcal, are associated with a reduced risk for developing AD.