Media release
From: Springer NatureMedicine: Shingles vaccine linked to reduced risk of dementia
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, reported 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 and colleagues have taken advantage of a policy in Wales that dictated eligibility for a vaccine against shingles, also known as herpes zoster. People born on or after 2 September 1933 were eligible for at least 1 year for the herpes zoster vaccination from 1 September 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 282,541 individuals born between 1 September 1925 and 1 September 1942. They 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 propose potential mechanisms to explain how zoster vaccination might reduce the risk of dementia, such as reduced reactivation of dormant zoster virus or a broader immune mechanism triggered by the vaccine. The authors note that further research in the form of a randomized trial is needed to conclusively test the effect of shingles vaccination on dementia and cognition. “Although it is still unclear precisely how herpes zoster vaccination lowers the risk of dementia, the implications of the study are profound,” notes Anupam Jena in an accompanying News & Views. “The vaccine could represent a cost-effective intervention that has public-health benefits strongly exceeding its intended purpose.”
Expert Reaction
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Dr Henry Brodaty is a Scientia Professor of Ageing and Mental Health and Co-Director of the Centre for Healthy Brain Ageing at the University of New South Wales
Dr Joseph Doyle is a Professor of Infectious Diseases at Monash University and President of the Australasian Society for Infectious Diseases