Databases from their inception to December 2022 were thoroughly searched, including PubMed, EMBASE, Cochrane Library, clinicaltrials.gov, and Web of Science for case–control, cross-sectional, or cohort studies investigating the association of Herpes zoster vaccination and dementia. We took the adjusted odds ratio (OR) and 95% confidence interval (CI) from each trial to analyze the relationship between the herpes zooster vaccine and the risk of dementia. Statistical analysis was performed on the retrieved adjusted OR and 95% CI using Stata v. 16.0 (Stata Corp, College Station, TX, USA). The Newcastle-Ottawa Scale (NOS) for nonrandomized studies was employed to rate the research' quality.

We included five  high-quality studies (1 cross-sectional, 1 case-control, 3 cohort) with 103,615 vaccinated patients.  The studies were all of high quality, ranging from 7 to 9. The average result was 8.4. A random effects model meta-analysis was used due to high heterogeneity (I2=98%, p<0.00001). Our data demonstrated that patients who had  Herpes zoster vaccination were at a significantly lower risk of developing dementia. Although a significant heterogeneity (I2 = 98%, p < 0.00001) was observed in the meta-analysis, a pooled OR was estimated at was 0.76 (95% CI: 0.60,0.96), p (overall effect) = 0.02], which indicated that Herpes zoster vaccination reduces the risk of dementia. 

Our Meta-analysis has demonstrated that Herpes zoster vaccination is significantly associated with reduction of risk of dementia.  However, more epidemiological studies and experiments are needed to understand the association of Herpes zoster vaccination and dementia.