A new international study has found that the shingles (herpes zoster) vaccine may not only help prevent dementia but could also slow its progression.
Researchers from Stanford University, Heidelberg Institute of Global Health and Cardiff University examined electronic health records from the Secure Anonymised Information Linkage (SAIL) databank, finding that people who were eligible for the live shingles vaccine (Zostavax) were less likely to develop mild cognitive impairment, an early sign of dementia. Those already diagnosed with dementia were also less likely to die from the disease.
The study used the UK National Health Service's rollout of the shingles vaccination program to design a natural experiment. The rollout made people eligible or ineligible for the vaccine based on their date of birth and allowed researchers to compare two nearly identical groups - those born just before and just after the eligibility cutoff.
The researchers analysed health records from over 300,000 people in Wales between 2013 and 2022.
Dr Haroon Ahmed, GP and Clinical Reader in Epidemiology at Cardiff University's School of Medicine, who was a member of the research team, said: "Our results suggest that the shingles vaccine could potentially prevent early memory decline and slow disease progression."
Because the vaccine is safe, affordable, and already widely available, this finding could have major implications for public health - although more research is needed to test our work and understand more about the potential protective effect the vaccine offers against dementia, particularly how and why it works.
The study found that vaccination significantly reduced new diagnoses of mild cognitive impairment and, among those already living with the disease, deaths due to dementia. The protective effect was stronger in women than in men, a pattern also seen in other studies of vaccine-related immune responses.
While the exact mechanism is not yet clear, the scientists believe that shingles vaccination may help by preventing reactivation of dormant viruses such as varicella zoster and herpes simplex, which are thought to contribute to brain inflammation and the buildup of harmful proteins linked to dementia. Another possibility is that the vaccine provides a broader boost to the immune system, which counteracts immune weakening in older age.
The researchers hope that this new research leads to further studies among younger populations, and stress that further research is needed to confirm the findings and better understand how the vaccine influences brain health.
This study builds on our previous work in which we have reported the shingles vaccine appears to have prevented or delayed dementia diagnoses. We are hoping to raise funds from philanthropy for a randomized trial of the off-patent live shingles vaccine to more conclusively put these findings to the test.
The research, The effect of shingles vaccination at different stages of the dementia disease course, was published in Cell.
