Landmark study suggests shingles vaccine may protect against dementia

Recent research has sparked renewed interest in the potential role of vaccines in preventing more than just infectious diseases. A new study published in Nature offers the strongest evidence yet that the shingles vaccine, which protects against developing shingles, may also lower the risk of dementia, suggesting a potential new tool for preventing cognitive decline​. This study analyzed data from over 282,000 individuals, making it one of the largest investigations of its kind. Private Health Management (PHM) summarizes the important takeaways from this landmark study.

What is shingles, and how might it be linked to dementia?

Shingles is triggered by the same virus (varicella-zoster) that causes chickenpox in childhood. Once infected with it, the virus remains dormant in our nerve cells for life. In some people, especially those with a weaker immune system, the virus can wake up later in life and cause shingles, a condition that brings a painful rash and can sometimes lead to lasting nerve damage. Over the past few years, several studies have suggested that shingles vaccination may be associated with a decreased risk of dementia, but these studies could not demonstrate a direct role for the vaccine without ruling out influence from other factors—like overall health or lifestyle.^1–3

A natural experiment provides robust evidence  

The latest research, led by a team from Stanford University, leveraged a policy in Wales that determined whether a person was eligible for shingles vaccine based on a specific birthdate: September 2, 1933. Individuals born just before this date were permanently ineligible for the vaccine, while those born just after this date became eligible for the vaccine for at least one year. Because individuals born just days apart are otherwise very similar, this setup mimicked the conditions of a randomized trial, the gold standard in medical research​.

Using electronic health record data, the researchers compared dementia diagnoses in these individuals over a seven-year follow-up period. They found that those who had received the live-attenuated shingles vaccine (Zostavax®) had a 20% lower risk of developing dementia than those who did not.⁴ This effect was especially pronounced in women. The study ruled out several alternative explanations for this effect. For example, the vaccine did not increase uptake of other preventive services, such as flu shots or doctor visits, nor did it affect the likelihood of being diagnosed with other common diseases. This strengthens the case that the vaccine itself is responsible for the reduction in dementia risk​.

Researchers point to two potential mechanisms for how the vaccine could help prevent dementia. First, it may reduce reactivation of the virus that causes shingles, which has been implicated in neuroinflammation and cognitive decline. Second, the vaccine may have broader effects on the immune system that provide neurological protection, even beyond its impact on the virus​.

While this study specifically focused on the older Zostavax vaccine, the newer Shingrix® vaccine, which uses a different formulation, has since replaced it in many countries. Whether Shingrix offers similar dementia protection remains to be seen and will require further research. In the meantime, this study adds to the growing body of evidence that vaccines may potentially aid in delaying or preventing dementia.

References

1. Impact of herpes zoster vaccination on incident dementia: A retrospective study in two patient cohorts | PLOS One. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0257405.
2. Lophatananon, A. et al. Shingles, Zostavax vaccination and risk of developing dementia: a nested case–control study—results from the UK Biobank cohort. BMJ Open 11, e045871 (2021).
3. Schnier, C., Janbek, J., Lathe, R. & Haas, J. Reduced dementia incidence after varicella zoster vaccination in Wales 2013-2020. Alzheimers Dement (N Y) 8, e12293 (2022).
4. Eyting, M. et al. A natural experiment on the effect of herpes zoster vaccination on dementia. Nature 1–9 (2025) doi:10.1038/s41586-025-08800-x.