For the past two centuries, vaccines have been important to prevent infections. The World Health Organization estimates that vaccinations will prevent 3-5 million deaths per year from diseases such as diphtheria, tetanus, influenza, measles and, more recently, Covid-19.
There has long been a broad scientific consensus that vaccines prevent or reduce the spread of infectious diseases, but there are new research suggesting that the impact on treatment may exceed the benefits of preventing infectious diseases.
A study published in the renowned journal Nature in April 2025 found appetite evidence that herpes zona (or shingles) could reduce the risk of dementia by 20% in the general population.
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We are a team of physicians with expertise in the clinical and basic sciences of neurodegenerative disorders and dementia.
The study considers it potentially opens the door to other breakthroughs in understanding and treating dementia and other degenerative disorders of the brain.
The role of vaccines in reducing the risk of dementia?
One of the major challenges researchers face when trying to study the effectiveness of vaccines is finding unvaccinated “control groups” for comparison. This is a group that resembles a vaccine group in all respects, except for the fact that they have not received an active vaccine. This is because it is unethical to assign some patients to a control group to deprive vaccine protection against diseases such as shingles.
Nature Research exploited the Welsh policy change that came into effect in 2013, stating that those born after September 2, 1933 were eligible for herpes shingles vaccinations for at least a year, and those born before the reduction date were not. The vaccine was administered to prevent shingles. This is a painful condition caused by the same virus that causes chicken po, which can be dormant in the body and reactivated in later years.
Related: Shingles vaccines may be directly protected against dementia, and tips can be researched
Researchers used policy changes as a kind of natural lab to study the effects of shingles vaccination on long-term health outcomes. In a statistically refined analysis of health records, the team found that the vaccine reduces the likelihood of developing dementia by a fifth in seven years. This means that those who receive the shingles vaccine are less likely to develop clinical dementia over a 7-year follow-up period, with women benefiting more than men.
This study design allowed researchers to compare the two groups without actively robbing one group of access to vaccination. The two groups were of comparable age and had similar medical comorbidities. That is, a similar proportion of other medical conditions such as diabetes and hypertension.
The findings of this and other related studies increase the likelihood that vaccines will play a broader role in experimental treatment outside the realm of infectious diseases.
These studies also raise provocative questions about how vaccines work and how the immune system potentially prevents dementia.
How vaccines are protected
One scientific explanation for the reduction in dementia caused by the herpes zoster vaccine is the direct protection against the herpes zoster virus, which may play a role in the worsening of dementia.
However, it is also possible that the vaccines have given them protection by activating the immune system and providing a “trained immunity” in which repeated exposure to the vaccine or virus strengthens the immune system.
This study did not distinguish between different types of dementia, including Alzheimer’s disease or dementia caused by stroke. Furthermore, researchers are unable to draw conclusive conclusions about possible mechanisms about how vaccines are protected from health record-only analysis.
The next step is a prospective, randomized, double-blind, placebo-controlled study (the “gold standard” in medical clinical trials) to directly examine how the herpes zoster vaccine compares placebo with its ability to reduce the risk of dementia over time. Such studies, like other potential treatments, are needed before vaccines are recommended for routine clinical use in the prevention of dementia.
Dementia challenges that bend corners
Dementia is a major non-communicable disease that is the leading cause of death worldwide.
A January 2025 survey provided the latest figures on lifetime dementia risk across a wide range of US subsets. Researchers estimate that the lifetime risk of dementia after age 55 is 42%. This is an estimate of more than twice as much as before. The risk of dementia was 4% by age 75 and 20% at age 85, with the majority of risks occurring after age 85. Researchers predicted that the number of new cases of dementia in the United States would double from about 514,000 in 2020 to one million in 2060.
Once considered a disease that is largely confined to developed countries, the detrimental effects of dementia have become apparent worldwide as life expectancy increases in many previous developing countries. Although dementia has a variety of clinical symptoms and underlying neurobiology, there are different forms of its ability to treat Alzheimer’s disease is the most common.
Prospective studies that specifically test how to change the way vaccines are given may benefit from studying a population of patients with specific types of dementia at the risk of future dementia.
Unfortunately, for the past two to three decades, the amyloid hypothesis of Alzheimer’s disease has dominated scientific conversations, assuming that accumulation of a protein called amyloid in the brain contributes to the disorder. As a result, most efforts in experimental treatment for Alzheimer’s disease have focused on drugs that reduce brain amyloid levels.
However, the results so far have been modest and disappointing. Two recently approved amyloid-resistant therapies have minimal effects on slowing down, are expensive and have potentially serious side effects. Furthermore, drugs currently approved by the Food and Drug Administration for clinical use do not reverse cognitive decline.
Research based on health records suggests that while previous virus exposure increases the risk of dementia, routine vaccines, including routine vaccines for tetanus, diphtheria, pertussis, pneumonia, and shingles, reduce the risk.
Innovation and open mind
Among scientists, they tend to stick to old and familiar models of disease, reluctant to move in more unconventional directions.
But the process of doing science is how to teach researchers like our humility, opening our minds to new information, learning from our mistakes, and that data will take us on the quest for effective and life-saving therapy.
Vaccines could be one of those routes that don’t run very often. It is an exciting possibility that it could open the door to other breakthroughs in understanding and treating brain degenerative disorders.
This edited article will be republished from the conversation under a Creative Commons license. Please read the original article.
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