For the last two hundred years, vaccines have played a vital role in preventing infectious diseases. The World Health Organization suggests that vaccination saves around 3 million to 5 million lives each year from illnesses like diphtheria, tetanus, influenza, measles, and more recently, COVID-19.
There’s been a long-standing scientific consensus on vaccines being effective in preventing the spread of infections, but recent studies indicate their benefits might extend beyond just infectious diseases.
A study published in April 2025 in the journal Nature presented intriguing findings that the herpes zoster, or shingles, vaccine could potentially reduce the risk of dementia in the general population by up to 20%.
We are a group of physician scientists specializing in clinical and basic science related to neurodegenerative disorders and dementia.
This study could pave the way for further advances in understanding and treating dementia and other brain degenerative disorders.
Do vaccines reduce dementia risk?
Researchers often struggle to find an unvaccinated “control group” for studies comparing the effects of vaccines. It’s difficult because it’s unethical to exclude some individuals from vaccination against diseases like shingles.
The study from Nature utilized a policy change in Wales, effective from 2013, which allowed individuals born on or after September 2, 1933, to receive the herpes zoster vaccination for at least a year, while those born earlier did not qualify.
This vaccine was aimed at preventing shingles, a painful condition caused by the same virus that leads to chickenpox, which can remain dormant in the body and reactivate later.
Using this policy change as a natural experiment, researchers analyzed health records and discovered that the shingles vaccine reduced the likelihood of developing dementia by one-fifth over a seven-year timeframe.
This suggests that those vaccinated were less likely to show signs of dementia over that period, with more significant benefits noted among women compared to men.
The study design enabled researchers to compare two similar groups without withholding vaccination from anyone. Both groups were of a similar age and had similar rates of medical conditions such as diabetes or high blood pressure.
Findings from this and related studies hint that vaccines might play a broader role in therapeutic applications beyond just combating infectious diseases.
These studies prompt thought-provoking questions about how vaccines function and whether our immune system might have a role in preventing dementia.
Understanding the protective effects of vaccines
One possible explanation for the shingles vaccine reducing dementia risk could be its direct protective effect against the shingles virus, which might contribute to exacerbating dementia.
There’s also a chance that the vaccine could strengthen the immune system through a mechanism known as “trained immunity,” where the immune response is enhanced by repeated exposure to vaccines or viruses.
The study didn’t clarify different types of dementia, such as those related to Alzheimer’s disease or strokes. Moreover, drawing firm conclusions about the underlying mechanisms from health records alone is challenging.
The logical next step would be to conduct a rigorous, randomized, double-blind, placebo-controlled study to directly assess how the herpes zoster vaccine affects dementia risk compared to a placebo over time.
Such research is crucial before any vaccines or other therapies can be generally recommended for preventing dementia.
Navigating the complexities of dementia
Dementia is a significant noncommunicable disease and a leading cause of mortality worldwide.
A January 2025 study revealed updated statistics on lifetime dementia risk across various segments of the U.S. population, with researchers estimating a lifetime risk of about 42% for those over 55—more than double previous estimates.
By age 75, the risk stands at 4%, increasing to 20% by age 85, with most risks manifesting after 85. Researchers forecast that the number of new dementia cases in the U.S. could double in the next four decades, from approximately 514,000 in 2020 to 1 million by 2060.
Once mainly seen as a condition limited to the developed world, dementia’s impacts are now evident globally, especially as life expectancy has risen in many countries that were once considered less developed.
While various forms of dementia have distinct clinical presentations and underlying biology, Alzheimer’s disease remains the most prevalent.
Prospective studies that specifically examine how vaccination affects future dementia risks might benefit from focusing on specific dementia types, as different variants could require unique treatment approaches.
Regrettably, the last few decades have seen the amyloid hypothesis of Alzheimer’s disease dominate much of the scientific dialogue; this hypothesis suggests that the buildup of amyloid protein in the brain is central to the disorder. Consequently, much of the research has focused on medications aimed at reducing amyloid levels.
However, results have often been modest and disappointing. Recently approved amyloid-lowering therapies have had limited effectiveness, are costly, and can lead to serious side effects. Currently, no FDA-approved drug successfully reverses cognitive decline.
Research indicates that past exposure to viruses might increase dementia risk, while routine vaccinations—against diseases like tetanus, diphtheria, pneumonia, and shingles—appear to lower that risk.
Embracing innovation and open-mindedness
Scientists sometimes have a tendency to cling to well-established ideas, reluctant to explore more unconventional avenues.
But, the nature of scientific inquiry often teaches humility, encouraging researchers to remain open to new data, learn from errors, and follow where the evidence leads, all in pursuit of life-saving treatments.
Vaccines might be an underexplored avenue worth pursuing. Their potential to unlock new understanding and treatments for degenerative brain disorders is an exhilarating prospect.
