A new study suggests that receiving the live shingles vaccine is associated with a slightly lower risk of developing memory disorders and Alzheimer’s disease in older adults. Scientists found that the vaccination might delay the onset of cognitive decline, providing evidence for benefits beyond just preventing shingles. The findings were recently published in the journal Alzheimer’s & Dementia.
The live zoster vaccine is a widely used immunization designed to prevent shingles in older populations. Shingles is a painful skin rash caused by the reactivation of the varicella zoster virus. This is the exact same virus that causes chickenpox in children. Once a person recovers from a childhood case of chickenpox, the virus retreats into the nervous system and goes dormant. As people age and their immune system naturally weakens, the virus can wake up and cause a shingles outbreak.
The varicella zoster virus is known to cause acute and chronic inflammation in the nervous system. Recent evidence suggests that this type of viral inflammation might play a role in the development of certain neurological conditions. Some scientists suspect that the virus could contribute to the brain changes associated with Alzheimer’s disease. By stopping the virus from waking up, the shingles vaccine might help protect the brain from related damage over time.
Scientists are also exploring the idea that live vaccines might offer broader health benefits than just preventing their specific target diseases. These extra benefits are known in the medical field as off target effects. Live vaccines contain a weakened, or attenuated, form of the virus, which stimulates a strong response from the body’s innate immune system. This general immune boost might train the body to better regulate inflammation, potentially protecting against various chronic diseases.
A few earlier studies pointed to a reduced risk of dementia after a shingles vaccination. The authors wanted to test this association in a much larger population over a longer period. Dr. Dong Keon Yon, a professor of pediatrics and digital health at Kyung Hee University College of Medicine in Seoul, South Korea, explained the rationale for the project. “We were initially interested in the possibility that live zoster vaccination may have broader health benefits beyond preventing shingles,” Yon said.
“Some previous research, including our own work, suggested that the vaccine might be associated with lower risks of several aging-related outcomes, such as cardiovascular disease and allergic or immune-related conditions,” Yon continued. “Given that varicella-zoster virus reactivation has also been linked to neuroinflammation and vascular injury, which are pathways relevant to cognitive decline, we wondered whether similar protective associations could be observed for cognitive disorders. This led us to examine whether zoster vaccination was associated with a reduced risk of memory disorders and Alzheimer’s disease in older adults.”
To test this idea, the researchers analyzed data from over two and a half million adults aged 50 and older in South Korea. They gathered this information by linking three national databases managed under the country’s universal health insurance system. This large scale integration allowed the authors to review medical claims, prescription records, national health examination results, and vaccination data between 2012 and 2024.
The team focused entirely on the live shingles vaccine, which is administered as a single dose in South Korea. They identified individuals who received the vaccine during the study period and compared them to individuals who had no record of the vaccination. To ensure a fair and accurate comparison, the researchers removed people who already had a documented history of memory disorders or dementia before the study began. They only tracked new medical diagnoses that occurred at least thirty days after the vaccination date.
The researchers used a specific statistical technique to balance the two groups based on their personal characteristics. This step ensured that the vaccinated and unvaccinated groups were highly similar in terms of age, sex, household income, and the region where they lived. They also matched the groups based on medical factors like body weight, blood pressure, fasting blood sugar, and preexisting conditions like high cholesterol or heart disease.
The statistical balancing also accounted for important lifestyle habits recorded during national health checkups. These habits included aerobic physical activity, smoking status, and weekly alcohol intake. After matching the participants, the final analysis included just over one million people. Exactly half of these individuals were in the vaccinated group, and the other half were in the unvaccinated control group.
The average age of the participants in the final analysis was about 62 years old, and slightly more than half were female. The authors tracked the health outcomes of these individuals for up to 12 years. To make sure their results were not influenced by general health differences between people who get vaccines and people who do not, the researchers also tracked unrelated medical events like appendicitis and hair loss.
The researchers found that receiving the live shingles vaccine was associated with a lower risk of developing cognitive conditions. People who received the vaccine had a 12 percent lower risk of developing memory disorders compared to those who were not vaccinated. They also showed a 25 percent lower risk of developing Alzheimer’s disease. The researchers did not find any association between the vaccine and the unrelated medical events like appendicitis, which suggests their main findings were accurate.
“One finding that stood out to us was the consistency of the association across cognitive outcomes,” Yon said. “The vaccinated group had lower risks of both memory disorders and Alzheimer’s disease, suggesting that the observed association was not limited to a single cognitive outcome.”
To better understand what these numbers mean in real life, the scientists calculated the average amount of time participants lived without developing these cognitive conditions. Over a ten year period, the vaccinated group lived without memory disorders for an average of about 15 and a half extra days compared to the unvaccinated group. For Alzheimer’s disease, the vaccinated group gained an average of just over 11 extra disease free days over a decade.
This specific timeframe suggests that the vaccine tends to slightly delay the onset of cognitive decline rather than completely preventing it. The timing of the protection also provided evidence for this idea. The strongest reduction in risk occurred during the first two to four years after the vaccination. The protective association slowly faded over time and disappeared entirely after six years.
The authors also looked at how lifestyle habits modified the effects of the vaccine. “We were also interested to see that the association appeared to vary over time and across lifestyle-related subgroups,” Yon said. “This pattern suggests that the potential benefits of vaccination may be connected to broader aspects of health and aging, rather than acting in isolation.”
They discovered that the protective association against Alzheimer’s disease was less pronounced among people who were current smokers. In a similar way, people who consumed alcohol regularly saw a reduced protective effect for both memory disorders and Alzheimer’s disease compared to non drinkers. Smoking and heavy drinking are known to weaken the immune system, which might explain why the vaccine appeared less effective in these groups.
When asked what the public should understand from these results, Yon offered a nuanced view. “The average person should take away that zoster vaccination may have benefits beyond preventing shingles,” Yon explained. “In our study, older adults who received the live zoster vaccine had a lower risk of developing memory disorders and Alzheimer’s disease, suggesting that vaccination may be linked to broader aspects of healthy aging.”
“At the same time, this does not mean that the zoster vaccine should be viewed as a dementia-prevention treatment,” Yon cautioned. “The practical message is that staying up to date with recommended vaccinations in older adulthood may be an important part of protecting long-term health, and cognitive health may be one area where these benefits deserve further study.”
“We think one important message is that vaccines in older adulthood should be viewed as a key part of preventive health,” Yon added. “The zoster vaccine is already important for preventing shingles and its complications, but our findings suggest that its potential relevance may extend to broader aspects of aging, including cognitive health.”
He also noted that brain health is complicated and depends on multiple systems. “At the same time, cognitive health is influenced by many factors, including vascular health, lifestyle, chronic disease management, and social factors,” Yon said. “Vaccination should be seen as one component of a broader strategy to support healthy aging.”
While the study provides evidence of a protective link, there are a few limitations to keep in mind. “As with any large real-world data study, the findings should be interpreted in the context of the study design,” Yon noted. “We used nationwide population-based data and applied several statistical approaches to make the vaccinated and unvaccinated groups as comparable as possible, but there may still be unmeasured factors that influence both vaccination and long-term cognitive health.”
For example, a person’s level of social engagement or the mental complexity of their daily work were not tracked in the national health databases. Some cases of early dementia or mild memory loss might have been missed entirely. This can happen if patients delay seeking medical care or if a doctor does not make a formal diagnosis during a standard visit.
The absolute difference in disease free days between the two groups was relatively small, despite the large percentage drop in relative risk. Also, the study only evaluated the live attenuated shingles vaccine. A newer, recombinant shingles vaccine is now widely used in many countries, including South Korea since 2022. Recombinant vaccines use just a small piece of the virus rather than a weakened whole virus, and it is not yet known if this newer type offers similar benefits for brain health.
Future research will need to track cognitive health in older adults over even longer periods. “Our long-term goal is to better understand how adult vaccination may contribute to healthy aging beyond the prevention of a single infectious disease,” Yon said. “For this line of research, an important next step is to examine whether similar associations are seen with recombinant zoster vaccines and in other populations outside Korea.”
The study, “Herpes zoster vaccination and cognitive disorders in older adults,” was authored by Jiyeon Oh, Kyeongmin Lee, Dongjin Yeo, Jaehyeong Cho, Tae Hyeon Kim, Jinseok Lee, Hayeon Lee, Ho Geol Woo, and Dong Keon Yon.
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