Does the shingles vaccine lower the risk of dementia?

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1. 1

   Association Between Herpes Zoster Vaccination and Dementia Risk: A Systematic Review and Meta-Analysis.

   Vaccines (Zhang et al.)Published Aug 10, 2026Checked Oct 4, 2026

   “Two regression-discontinuity studies reported eligibility-associated absolute reductions in dementia diagnosis of 1.3 and 1.8 percentage points. Two direct vaccine comparisons favored the recombinant zoster vaccine (RZV; Shingrix) over the live attenuated vaccine (ZVL; Zostavax) (RMTL ratio = 0.83; 95% CI: 0.80-0.87; RR = 0.82; 95% CI: 0.69-0.98). The only direct dose comparison favored two or more RZV doses over one dose (RR = 0.81; 95% CI: 0.74-0.88). Active-comparator associations were generally attenuated, whereas age- and subtype-specific findings varied. These secondary findings were exploratory.ConclusionsHZV was associated with lower dementia risk in observational studies, with directionally consistent quasi-experimental findings. Direct evidence suggested potentially stronger inverse associations for RZV and complete vaccination, but was based on few independent data sources. Substantial heterogeneity and residual confounding preclude causal interpretation, and further prospective or randomized evidence is needed.”

2. 2

   Dementia Risk After Recombinant Herpes Zoster Vaccination in Older Adults With a Recent Skilled-Nursing Facility Stay : A Target Trial Emulation.

   Annals of internal medicine (Hayes et al.)Published Jun 16, 2026Checked Oct 4, 2026

   “ata.ParticipantsMedicare fee-for-service beneficiaries aged 66 years or older who were admitted to a skilled-nursing facility between 1 January 2017 and 31 December 2022, had linked EHR data, had no diagnosed dementia, and were eligible for RZV.InterventionReceipt of at least 1 RZV in the facility or, if discharged, by 12 months after admission versus no receipt of RZV.MeasurementsValidated dementia diagnosis and 57 baseline and time-varying covariates.ResultsThe study cohort included 509 926 participants (mean age, 79 years); 8843 (1.73%) received at least 1 RZV dose within 12 months after admission, and of these, 87.0% received RZV after discharge. Receipt of RZV was associated with risk for dementia being 5.8 percentage points lower (95% CI, 3.9 to 7.5 percentage points lower; risk ratio, 0.76 [CI, 0.69 to 0.84]; 4-year risk, 18.8% with ≥1 RZV vs. 24.6% with no RZV). Associations were attenuated in men and those with prior live HZ vaccination.LimitationNegative control analyses suggest some residual confounding.ConclusionReceipt of RZV during admission to a skilled-nursing facility or within 12 months was associated with lower dementia risk.Primary funding sourceGlaxoSmithKline.”

3. 3

   Natural experiments of herpes zoster vaccination: Quantifying the implied vaccine effectiveness against dementia.

   Brain, behavior, and immunity (Kivimäki et al.)Published Sep 17, 2026Checked Oct 4, 2026

   “ded the theoretical maximum effectiveness of 100%, while the third non-Welsh estimate was also implausibly large; even under very high assumed vaccine effectiveness, explaining these findings would require underlying dementia risks among individuals vaccinated because of eligibility to be 1.7-2.3 times higher than in vaccine-ineligible populations, an unlikely scenario. The implied reductions in mild cognitive impairment and dementia-related mortality associated with vaccination were also large, at 41% and 56%, respectively. If vaccination reduced dementia risk by effects of the magnitude implied by these natural experiments, a decline might be expected in population-level dementia incidence following implementation of herpes zoster vaccination programmes; however, no corresponding decline was observed in national data from the UK, Australia, or Canada. In conclusion, the reported natural experiments on herpes zoster vaccination and dementia cannot be considered strong evidence of a clinically meaningful effect; their implied vaccination effects are internally inconsistent and, in some cases, impossible or biologically implausible, highlighting the need for independent replication.”

4. 4

   Efficacy and Effectiveness of the Recombinant Zoster Vaccine Against Herpes Zoster, Herpes Zoster Ophthalmicus, Postherpetic Neuralgia and Dementia: A Systematic Review and Meta-Analysis.

   Reviews in medical virology (Heen et al.)Published Sep 1, 2026Checked Oct 4, 2026

   “We synthesised the latest evidence on long-term effects, incorporating recent data from both trials and real-world effectiveness studies. A total of 27 publications based on 18 primary studies, 3 randomised controlled trials (RCTs) and 15 observational studies, were included. RZV provides very high protection against HZ in immunocompetent adults ≥ 50 years in RCTs, with approximately 95% efficacy and high certainty of evidence (CoE) according to GRADE. Observational studies also consistently indicate substantial protection, but effect estimates vary across settings (high CoE). Among vaccinated individuals who develop HZ, RZV is associated with reduced loss of quality of life and decreased analgesic use. The vaccine also substantially reduces the risk of herpes zoster ophthalmicus (HZO) (high CoE) and likely postherpetic neuralgia (PHN) (moderate CoE). Long-term follow-up suggests durable protection for at least 11 years (low CoE). RZV may be associated with a reduced risk of dementia (low CoE), due to uncertainty the true effect may be substantially different, and similar associations have been observed with other vaccines and may be confounded by healthy vaccinee bias.”

5. 5

   Infection, vaccination and risk of dementia: a proposed immunological model.

   Frontiers in immunology (Devine et al.)Published Mar 4, 2026Checked Oct 4, 2026

   “Whilst the mechanisms behind this remain unclear, intriguing epidemiological data suggest that several vaccinations are correlated with reduced risk for dementia. Intravesicular administration of the tuberculosis vaccine strain Bacille Calmette-Guérin (BCG) has been associated with decreased risk of dementia in bladder cancer patients. This has led to the hypothesis that non-specific effects of vaccinations, mediated through trained innate immunity, provide a mechanistic explanation. Over the last few years, the AS01-adjuvanted recombinant shingles vaccine has also been associated with reduced risk in several studies. Moreover, in a recent study, immunization with the adjuvanted RSV vaccine, also containing AS01, was shown to reduce risk of dementia. Integrating data on BCG and mechanistic hypotheses, recent findings on the AS01 adjuvant, and the role of trained innate immunity, we describe here an immunological model that connects vaccine and adjuvant mode of action with risk of dementia. This immunological model can help shape a research roadmap to further elucidate the mechanisms behind the collective epidemiological data.”