Shingles Vaccine Linked to Lower Dementia Risk in New Study

A recent study led by researchers at Stanford Medicine has revealed that the shingles vaccine may significantly reduce the risk of developing dementia. This groundbreaking research, published on April 2, 2025, in the journal Nature, analyzed health records from older adults in Wales and found that those vaccinated against shingles were 20% less likely to develop dementia over a seven-year period compared to those who did not receive the vaccine.

The findings support an emerging theory that viral infections affecting the nervous system might contribute to the onset of dementia. If validated through further studies, this could indicate that a preventive measure for dementia is already available. In a related study set to publish on December 2, 2025, the researchers also discovered that the shingles vaccine may benefit individuals already diagnosed with dementia, potentially slowing the progression of the disease.

Understanding Shingles and Its Connection to Dementia

Shingles is caused by the varicella-zoster virus, the same virus responsible for chickenpox. After contracting chickenpox, the virus remains dormant in the nerve cells and can reactivate later in life, especially in older individuals or those with weakened immune systems. With more than 55 million people affected globally, dementia remains a pressing public health concern, with an estimated 10 million new cases diagnosed each year.

Historically, research on dementia has focused on the accumulation of plaques and tangles in the brains of individuals with Alzheimer’s disease, the most common form of dementia. Despite extensive studies, breakthroughs in prevention or treatment have been elusive, prompting some researchers to explore the potential influence of viral infections, including shingles.

Previous studies suggested a correlation between the shingles vaccine and reduced dementia rates. However, these studies faced criticism for potential biases, as vaccinated individuals often exhibit healthier lifestyles that are difficult to measure. Pascal Geldsetzer, MD, PhD, assistant professor of medicine and senior author of the new study, noted that such studies lacked the rigor necessary to support definitive recommendations.

A Natural Experiment in Vaccine Rollout

Two years ago, Geldsetzer identified a “natural experiment” in the vaccination rollout in Wales that mitigated bias. The shingles vaccine, which was live-attenuated, was made available to individuals who turned 79 on or after September 1, 2013. Those who were 80 or older on that date were ineligible for the vaccine, creating a clear distinction based on age.

By comparing health records of over 280,000 older adults aged 71 to 88 who did not have dementia at the start of the vaccination program, researchers could effectively isolate the impact of vaccination. The analysis focused on individuals who turned 80 just before and just after the eligibility cutoff, ensuring comparability in health profiles.

“We know that if you take a thousand people at random born in one week and a thousand people at random, born a week later, there shouldn’t be anything different about them on average,” said Geldsetzer. This approach provided a level of rigor akin to a randomized controlled trial, allowing researchers to analyze the health outcomes of both groups over a seven-year period.

The study reported that approximately 50% of those eligible received the vaccine, while very few ineligible individuals did. The vaccinated group experienced a reduction in shingles occurrences by about 37% over the same period. By 2020, one in eight older adults aged 86 to 87 had been diagnosed with dementia; however, those vaccinated against shingles exhibited a 20% lower likelihood of developing the condition.

The researchers ruled out numerous variables that could affect dementia risk, finding that the only notable difference between the two groups was the rate of dementia diagnoses. The results suggest that vaccination may play a crucial role in protecting against the disease.

Potential Therapeutic Benefits and Future Research

Further analysis revealed that the shingles vaccine’s protective benefits extended beyond preventing dementia to potentially slowing disease progression in those already diagnosed. Individuals who received the vaccine displayed a lower likelihood of being diagnosed with mild cognitive impairment and demonstrated a reduced mortality rate associated with dementia.

Of the 7,049 Welsh seniors with dementia at the start of the vaccination program, nearly half died from the disease during follow-up. In contrast, only about 30% of those who had been vaccinated succumbed to dementia.

Geldsetzer expressed excitement over the implications of these findings, stating, “This really suggests the shingles vaccine doesn’t have only preventive, delaying benefits for dementia, but also therapeutic potential for those who already have dementia.” Furthermore, the study showed that women benefited from the vaccine’s protective effects against dementia more than men, possibly due to immune response differences.

The research team hopes that these findings will encourage greater investment in studies exploring the link between vaccinations and dementia prevention. They have replicated the results in health records from other countries, including England, Australia, New Zealand, and Canada, continuing to observe a strong protective signal for dementia across multiple datasets.

Geldsetzer is now pursuing funding for a large, randomized controlled trial to solidify the causal relationship between the shingles vaccine and dementia outcomes. Such a trial would involve participants being randomly assigned to receive either the vaccine or a placebo, providing definitive evidence in support of these compelling findings.

The study received funding from several reputable organizations, including The Phil & Penny Knight Initiative for Brain Resilience and the National Institute on Aging. As research in this area progresses, the potential for the shingles vaccine to change the landscape of dementia prevention and treatment remains a hopeful prospect.