The shingles vaccine reduced the probability of new dementia diagnoses by around one-fifth over seven years, according to a large-scale study of a population in Wales, UK. The results were published in Nature. This finding suggests that the vaccine could be a cost-effective strategy for preventing or delaying dementia. However, further research is needed to determine whether the observed effects are truly causal and to understand how protection is conferred.
Recent studies have found associations between herpes virus infections and an increased risk of developing dementia, including Alzheimer’s disease, raising the question of whether vaccination might have a protective effect. However, testing this hypothesis is challenging, requiring large, matched populations of vaccine recipients and control individuals, along with a long follow-up period.
To overcome common bias concerns, Pascal Geldsetzer from Stanford University and others took advantage of a policy in Wales that dictated eligibility for a vaccine against shingles, also known as herpes zoster. People born on or after September 2, 1933 were eligible for at least one year for the herpes zoster vaccination from September 1, 2013, whereas those born before this date were not eligible. This unique policy allowed the authors to compare vaccine-eligible to vaccine-ineligible individuals who differed in their age by merely a few weeks and were, thus, expected to be similar in all characteristics.
The authors used electronic health data to compare new dementia diagnoses between the vaccine-eligible and ineligible population in a cohort of 2,82,541 individuals born between 1 September 1925 and 1 September 1942. According to a release, the researchers found that receiving the herpes zoster vaccine decreased the relative probability of a new diagnosis of dementia within the seven-year follow up period by approximately 20%. This effect was greater in women than in men.
The percentage of adults who received the vaccine was 0.01% in those merely one week too old to be eligible but rose to 47.2% amongst those born just one week after the eligibility date. Apart from this increase in vaccine uptake, the two populations, aged merely a few weeks apart, are unlikely to differ systematically, thereby greatly reducing the likelihood of bias in the analysis.
The authors note that further research in the form of a randomised trial is needed to conclusively test the effect of shingles vaccination on dementia and cognition.
Published – April 05, 2025 11:00 pm IST
