Neurology
The effect of herpes zoster vaccination on the occurrence of deaths due to dementia in England and Wales Felix Michalik* Pascal Geldsetzer Felix Michalik Min Xie Markus Eyting Simon Heß Seunghun Chung
Background: Using a unique natural randomization, we have recently provided evidence from Welsh electronic health record data that HZ vaccination caused a reduction in new dementia diagnoses over a seven-year period. This study aimed to determine whether eligibility for HZ vaccination also caused a reduction in deaths due to dementia in England and Wales over a nine-year follow-up period.
Methods: Adults who had their 80th birthday shortly before September 1 2013 were ineligible for free HZ vaccination and remained ineligible for life, whereas those who had their 80th birthday shortly after September 1 2013 (i.e., born on or after September 2 1933) were eligible for one year. This date-of-birth threshold generated birth cohorts who are likely exchangeable in observed and unobserved characteristics except for a small difference in age and a large difference in HZ vaccination uptake. We used country-wide data from death certificates in England and Wales on underlying causes of death from September 1 2004 to August 31 2022 by ICD-10 code and month of birth. Our analysis compared the percentage of the population with a death due to dementia among the month-of-birth cohorts around the September 2 1933 eligibility threshold using a regression discontinuity design.
Results: The study population included 5,077,426 adults born between September 1 1925 and August 31 1941 who were alive at the start of the HZ vaccination program. We estimated that over a nine-year follow-up period, eligibility for HZ vaccination reduced the percentage of the population with a death due to dementia by 0.38 (95% CI: 0.08 to 0.68, p=0.012) percentage points, corresponding to a relative reduction of 4.8%. As in our prior analysis, this effect was stronger among women (-0.62 [95% CI: -1.06 to -0.19] percentage points, p=0.004) than among men (-0.11 [95% CI: -0.51 to 0.28] percentage points, p=0.574).
Conclusions: Our findings indicate that HZ vaccination improved cognitive function at a fairly advanced stage of the dementia disease process because most individuals whose underlying cause of death was dementia during our nine-year follow-up period were likely already living with dementia at the start of the HZ vaccination program.
