New research suggests that live shingles vaccine slightly reduces the risk of developing memory loss and Alzheimer’s disease in older adults. Scientists have found that vaccination may delay the onset of cognitive decline, providing evidence of benefits beyond preventing shingles. The results of this study were recently published in the journal Alzheimer’s disease and dementia.
Live shingles vaccine is a widely used vaccination to prevent shingles in older adults. Shingles is a painful rash caused by reactivation of the varicella-zoster virus. This is the exact same virus that causes chickenpox in children. When a person recovers from childhood chickenpox, the virus retreats into the nervous system and becomes dormant. As people age and their immune systems naturally weaken, 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 may play a role in the development of certain neurological conditions. Some scientists suspect that the virus may contribute to the brain changes associated with Alzheimer’s disease. By blocking the virus from awakening, the shingles vaccine may help protect the brain from long-term related damage.
Scientists are also exploring the idea that live vaccines may offer broader health benefits than just preventing specific target diseases. These additional benefits are known in the medical field as off-target effects. Live vaccines contain a weakened or attenuated form of the virus that stimulates a strong response from the body’s natural immune system. This overall immunity boost trains the body to better control inflammation, which may protect against a variety of chronic diseases.
Several previous studies have noted a reduced risk of dementia after shingles vaccination. The authors wanted to test this association over a longer period of time in a larger population. Dr. Dong Keon Yen, professor of pediatrics and digital health at Kyung Hee University School of Medicine in Seoul, South Korea, explained the rationale for the project. “We were initially interested in the possibility that live shingles vaccination could provide a wide range of health benefits beyond preventing shingles,” Yong said.
“Several previous studies, including our own, have suggested that vaccines may be associated with a reduced risk of several aging-related outcomes, such as cardiovascular disease and allergy- or immune-related diseases,” Yong continued. “Given that varicella-zoster virus reactivation is also associated with neuroinflammation and vascular damage, pathways associated with cognitive decline, we wondered if a similar protective association might be observed with cognitive impairment. This led us to examine whether shingles vaccination is associated with a lower risk of memory loss and Alzheimer’s disease in older adults.”
To test this idea, researchers analyzed data from more than 2.5 million South Korean adults aged 50 and older. They gathered this information by linking three national databases managed under the country’s universal healthcare system. This large-scale integration allowed the authors to review medical claims, prescription records, national health examination results, and vaccination data from 2012 to 2024.
The research team focused entirely on a single-dose live shingles vaccine in South Korea. They identified individuals who received the vaccine during the study period and compared them to individuals with no record of vaccination. To ensure a fair and accurate comparison, the researchers excluded people with existing records of memory loss or dementia before the study began. They only tracked new medical diagnoses that occurred at least 30 days after the vaccination date.
The researchers used specific statistical techniques to balance the two groups based on individual characteristics. This step ensured that the vaccinated and unvaccinated groups were very similar in terms of age, gender, household income, and area of residence. They also matched the groups based on medical factors such as weight, blood pressure, fasting blood sugar levels, and pre-existing conditions such as high cholesterol or heart disease.
The statistical balance also takes into account important lifestyle habits recorded in the National Health Checkup. These habits include aerobic exercise, smoking status, and weekly alcohol intake. After matching participants, the final analysis included just over 1 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 participants in the final analysis was approximately 62 years, and just over half were female. The authors tracked the health of these people for up to 12 years. To ensure that the study results were not influenced by differences in general health conditions between vaccinated and non-vaccinated people, the researchers also tracked unrelated medical events such as appendicitis and hair loss.
Researchers found that receiving the live shingles vaccine was associated with a lower risk of developing cognitive symptoms. Those who received the vaccine had a 12 percent lower risk of developing memory problems than those who did not receive the vaccine. It also showed a 25% lower risk of developing Alzheimer’s disease. Researchers found no link between the vaccine and unrelated medical events such as appendicitis. This suggests that their main finding was accurate.
“One of the notable findings for us was the consistency of the associations across cognitive outcomes,” Yong said. “The vaccinated group had a lower risk of both memory impairment and Alzheimer’s disease, suggesting that the observed associations are not limited to a single cognitive outcome.”
To better understand what these numbers mean in real life, scientists calculated the average amount of time participants lived without developing these cognitive conditions. Over a 10-year period, the vaccinated group lived on average about 15 and a half days longer without memory loss than the unvaccinated group. For Alzheimer’s disease, the vaccinated group gained an average of just over 11 disease-free days over 10 years.
This specific period of time suggests that the vaccine tends to slightly delay the onset of cognitive decline, rather than completely preventing it. The timing of protection also supported this idea. The strongest reduction in risk occurred during the first 2 to 4 years after vaccination. The conservation group gradually faded over time and disappeared completely six years later.
The authors also looked at how lifestyle changes the effectiveness of vaccines. “We were also interested in how this association appeared to change over time and across lifestyle-related subgroups,” Yong said. “This pattern suggests that the potential benefits of vaccination do not act in isolation but may be linked to broader aspects of health and aging.”
They found that the protective association against Alzheimer’s disease was less pronounced among people who currently smoked. Similarly, people who regularly consumed alcohol were found to have reduced protection against both memory loss and Alzheimer’s disease compared to non-drinkers. Smoking and heavy drinking are known to weaken the immune system, which may explain why vaccines appear to be less effective in these groups.
When asked what the public should understand from these results, Yong offered a mixed opinion. “The public should understand that the shingles vaccination may have benefits beyond preventing shingles,” Yong explained. “Our study shows that older adults who received the live shingles vaccine had a lower risk of developing memory loss and Alzheimer’s disease, suggesting that vaccination may be associated with broader aspects of healthy aging.”
“At the same time, this does not mean that the shingles vaccine should be considered a preventative treatment for dementia,” Yong cautioned. “The practical message is that staying up-to-date with recommended vaccinations into older adults may be an important part of protecting long-term health, and cognitive health may be one area where these benefits merit further study.”
“We think one of the key messages is that vaccines in older adults should be considered an important part of preventive health,” Yong added. “While the shingles vaccine is already important for preventing shingles and its complications, our findings suggest that its potential relevance may extend to broader aspects of aging, including cognitive function.”
He also pointed out that brain health is complex 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,” Yong said. “Vaccination should be seen as one element of a broader strategy to support healthy aging.”
Although this study provides evidence of a protective link, there are some limitations to keep in mind. “As with any large-scale real-world data study, the results should be interpreted in the context of the study design,” Yon said. “Although we used national population-based data and applied several statistical approaches to make vaccinated and unvaccinated groups as comparable as possible, there may still be unmeasured factors that influence both vaccination and long-term cognitive health.”
For example, an individual’s level of social engagement or the mental complexity of their daily tasks were not tracked in national health databases. Some cases of early dementia or mild memory loss may be completely missed. This can occur if a patient delays seeking medical care or if a doctor does not make a formal diagnosis during a routine examination.
Despite the significant reduction in relative risk, the absolute difference in disease-free days between the two groups was relatively small. Additionally, only a live attenuated herpes zoster vaccine was evaluated in this study. A new recombinant shingles vaccine is now being widely used in many countries, including South Korea, starting in 2022. Recombinant vaccines use only small pieces of virus rather than whole, attenuated viruses, but it is still unclear whether this new type offers similar benefits for brain health.
Future research should track older adults’ cognitive health over longer periods of time. “Our long-term goal is to go beyond prevention of single infectious diseases to better understand how adult vaccination contributes to healthy aging,” Yong said. “An important next step for this line of research is to examine whether similar associations are seen with recombinant shingles vaccines and other populations outside of Korea.”
The study, “Herpes Zoster Vaccination and Cognitive Impairment in the Elderly,” was authored by Jiyong Oh, Kyungmin Lee, Dongjin Yeo, Jaehyun Cho, Tae Hyun Kim, Jinseok Lee, Hayoung Lee, Heo Gol Woo, and Dong Keong Yong.
