Rebecca Araujo

Urban Health Today

A study in Nature reported that shingles vaccination was associated with a 20% reduction in risk of dementia over the 7 years after inoculation.Pascal Geldsetzer, MD, MPH, PhD, of Stanford University, and colleagues used electronic health record data from patients in Wales to compare probability of new dementia cases with and without zoster vaccination.&ldquo;To provide causal as opposed to correlational evidence, we take advantage of the fact that, in Wales, eligibility for the zoster vaccine was determined on the basis of an individual&rsquo;s exact date of birth,&rdquo; the authors noted. Individuals who were born after September 2, 1933, were ineligible for the vaccine and remained ineligible for life, whereas anyone born on or after that date was eligible to receive the vaccine for at least 1 year. Rates of vaccination were 0.01% among patients who were older than the cutoff date by just 1 week and 47.2% among those who were born just 1 week after the cutoff date.Over the 7-year follow-up period from time of vaccination, the zoster vaccine was associated with a reduction in likelihood of developing dementia by 3.5 percentage points (95% CI, 0.6-7.1; P=0.019), which corresponds to a 20.0% relative reduction in risk (95% CI, 6.5-33.4). In addition, the protective effect was stronger in women than in men.<h2>How the Shingles Vaccine Reduces Dementia Risk</h2>The researchers pointed to 3 potential mechanisms that could lead to the zoster vaccine offering a protective effect against dementia:<ul>
<li>Changes in healthcare use after a shingles episode</li>
<li>Reduced reactivation of the varicella zoster virus (VZV)</li>
<li>A VZV-independent immunomodulatory effect</li>
</ul>An averted shingles episode due to zoster vaccination could mean fewer opportunities for the healthcare system to diagnose dementia in the future. However, the authors noted that &nbsp;&ldquo;the size of our effect estimates for reductions in shingles episodes from zoster vaccination were considerably too small to plausibly account for the observed reduction in dementia diagnoses.&rdquo;The researchers investigated whether reductions in VZV reactivations are related to reduced risk of dementia. They found that reductions in dementia incidence emerged after more than 1 year from vaccination, implying that the protective effect occurred after the immunity boost against VZV. In addition, there was a higher incidence of dementia among individuals with multiple shingles episodes, and antiviral treatment of a shingles episode was associated with reduced incidence of dementia.Regarding a potential VZV-independent immunomodulatory effect, they pointed to the stronger benefit in dementia reduction among women, as there was no sex-based difference in performance of the vaccine on diagnoses of shingles. They also observed evidence of a stronger effectiveness of the vaccine against dementia in patients without autoimmune or allergic conditions. &ldquo;Thus, if the protective effect of zoster vaccination for dementia is mainly driven through a reduction of clinical and subclinical virus reactivations, then those with an autoimmune condition will likely benefit equally or more than those without such a condition,&rdquo; they explained.The authors acknowledged that these analyses are exploratory and that the mechanisms described are not mutually exclusive.In summary, they wrote, &ldquo;Through the use of a unique natural experiment, this study provides evidence of a dementia-preventing or dementia-delaying effect from zoster vaccination that is less vulnerable to confounding and bias&nbsp;than the existing associational evidence.&rdquo;Source: <a href="https://www.nature.com/articles/s41586-025-08800-x" target="_blank" rel="noopener">Nature</a>

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Shingles vaccination was associated with a 20% reduction in risk of dementia in the 7 years after inoculation. 