--- title: Could the Shingles Vaccine Help Prevent Dementia? description: The shingles vaccine has a potential protective effect against dementia, write Harvard doctors Christopher Worsham and Anupam Jena. canonical: https://time.com/7275048/shingles-vaccine-dementia-christopher-worsham-anupam-jena/ author: TIME article:opinion: true article:content_tier: free article:published_time: 2025-04-04T17:32:00.000Z article:modified_time: 2026-10-19T07:51:21.655Z article:section: Ideas og:title: Could the Shingles Vaccine Help Prevent Dementia? og:description: The shingles vaccine may have a protective effect against dementia, write doctors Christopher Worsham and Anupam Jena. og:url: https://time.com/7275048/shingles-vaccine-dementia-christopher-worsham-anupam-jena/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt64e6170c7107e5eb/6998c58c25f3ee2736644849/shingles-vaccine.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 2121 og:image:height: 1193 og:image:alt: vaccine og:type: article twitter:card: summary_large_image twitter:title: Could the Shingles Vaccine Help Prevent Dementia? twitter:description: The shingles vaccine may have a protective effect against dementia, write doctors Christopher Worsham and Anupam Jena. twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt64e6170c7107e5eb/6998c58c25f3ee2736644849/shingles-vaccine.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # Could the Shingles Vaccine Help Prevent Dementia? > Sponsored content. 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[Watch (HLS stream): Could the Shingles Vaccine Help Prevent Dementia?](https://cdn.jwplayer.com/manifests/qiY3zB68.m3u8) (3:00)  _Published 2025-04-07. If your doctor told you that a vaccine against dementia was available, would you be interested? According to a study published April 2, 2025 in the journal Nature by researchers in the U.S. and Germany, this question might not be hypothetical anymore._ by [Christopher M. Worsham](https://time.com/author/7198766/) and [Anupam Jena](https://time.com/author/anupam-b-jena/) Apr 4, 2025 5:32 PM UTC If your doctor told you that a vaccine against dementia was available, would you be interested? According to a study published April 2, 2025 in the journal Nature by researchers in the U.S. and Germany, this question might not be hypothetical anymore. by [Christopher M. Worsham](https://time.com/author/7198766/) and [Anupam Jena](https://time.com/author/anupam-b-jena/) Apr 4, 2025 5:32 PM UTC If your doctor told you that a vaccine against dementia was available, would you be interested? According to a [study](https://www.nature.com/articles/s41586-025-08800-x) published April 2 in the journal _Nature_ by researchers in the U.S. and Germany, this question might not be hypothetical anymore. The varicella-zostervirus—which causes varicella (chickenpox) in childhood and zoster (shingles) after lying dormant in nerve cells and re-activating later in life—is one virus that scientists have [hypothesized](https://www.nature.com/articles/s41380-021-01138-6) can cause dementia, because it infects the nervous system. We have vaccines against both conditions. The chickenpox vaccine protects children from the initial viral infection, and the separate shingles vaccine prevents the virus from reactivating in previously infected adults (which is most adults born before widespread chickenpox vaccination began in the late 1990s), stopping it from causing the painful shingles rash. The traditional way to find out if vaccinating adults against this virus could prevent dementia later in life would be to conduct a randomized controlled trial. We’d take a group of adults and randomly divide them into two groups: the “control” group that would get no vaccine, and the “intervention” group that would get the vaccine. Then, we’d look to see if there was a difference in rates of dementia between the two groups over time. The [problem](https://www.nature.com/articles/d41586-025-00861-2) here is that because dementia is a disease of old age, we’d have to closely follow thousands of patients, collecting health information over many years—which is no simple task. The researchers behind this new study, including Markus Eyting and Pascal Geldsetzer of Stanford University, didn’t do any of this, though. They were clever enough to realize this experiment had already happened—purely by accident—yet its results remained a mystery waiting to be uncovered. Back in 2013, the government of Wales decided that it would begin providing the zoster vaccine to prevent shingles in adults born on or after September 2, 1933, while those older than that would _not_ be eligible. Someone who was born on September 4, 1933 could get the vaccine, while someone born just a week earlier on August 28, 1933 was ineligible. **Read More**: [_The New CDC Study on Vaccines and Autism Should Take a Radical Approach_](https://time.com/7272138/cdc-study-vaccines-autism-adversarial-collaboration-essay/) Since the precise week we’re born is arbitrary, Welsh adults born just before versus just after the cutoff were similar to one another except for whether or not they were eligible to receive the vaccine. They were essentially randomized to either get the shingles vaccine or not. This phenomenon of patients getting accidentally randomized to one treatment or another is called a natural experiment—science happening “in the wild” without any researcher guiding it. Natural experiments like this one happen all the time, but they often go unnoticed unless researchers unearth them from existing data. Since years had passed since the vaccination program launched, researchers could look at health records of Welsh adults to see who developed dementia and who didn’t since 2013\. What they found was astounding. Because they were ineligible, almost nobody born just before the cutoff got the shingles vaccine. Meanwhile, about half of those born just after the cutoff received the vaccine, and accordingly, they had lower rates of shingles (because the primary benefit of the vaccine is to reduce the risk of developing shingles). But surprisingly, those who were eligible for vaccination also had a significantly lower rate of being diagnosed with dementia. The researchers estimated a nearly 20% reduction in dementia diagnosis among those who were, by chance, vaccinated. As remarkable as this analysis was, it doesn’t tell us exactly _why_ the shingles vaccine may have led to lower rates of dementia diagnosis. The most obvious explanation would be that if the reactivation of the virus during a shingles episode predisposes someone to developing dementia, preventing reactivation with the vaccine would reduce the risk of developing dementia. The researchers found evidence supporting this hypothesis. First, those who had more shingles episodes (and thus more viral reactivations) had higher rates of dementia. And second, they found that those who received antiviral medication for shingles episodes—which helps shut down the reactivation—had lower rates of dementia compared to those who didn’t get an antiviral medication. **Read More**: [_Why Do Taxi Drivers Have a Lower Risk of Alzheimer’s?_](https://time.com/7206222/taxi-drivers-alzheimers-disease-christopher-worsham-anupam-jena/) Another explanation could be that there’s something about the body’s response to the vaccine itself that protects against dementia. Vaccines work by stimulating the immune system, and that immune response could theoretically impact the brain in a way that reduces dementia risk. Researchers found two pieces of evidence suggesting this may be a factor. First, they found that those who had recently received a flu vaccine when they received their shingles vaccine were even more protected against dementia than those who only got the shingles vaccine. Second, they decided to look at differences between men and women, who have been shown to have different immune responses to vaccines. (Women may have [stronger immune responses](https://www.nature.com/articles/s41577-020-0338-x) to vaccination than men). They found that the protective effect against dementia was much larger among women than men. Any number of these mechanisms could explain the shingles vaccine’s potential protective effect against dementia. (One of us, Jena, explored these in depth in a [commentary](https://www.nature.com/articles/d41586-025-00861-2) published in _Nature_ alongside the study.) Clearly there’s more research to do to fully understand what’s happening here, but this study has provided a new road map to guide future investigation. This advance in our understanding of the zoster vaccine, shingles, and dementia wouldn’t have happened without these researchers recognizing the conditions for a natural experiment in Wales and carefully analyzing the data to understand what happened to these patients who, by chance, received the zoster vaccine. In an age where data are collected in nearly every aspect of our lives, troves of natural experiments in health care are waiting to be uncovered—as long as researchers have the opportunity and resources to find and analyze them. ## Transcript [00:00] So, Babu, you're a bit older than I am. [00:03] Have you ever had shingles? [00:05] I'm not that much older, first of all. [00:07] No, I haven't had shingles yet. [00:08] So I drew the short straw a couple of years ago and got shingles in [00:13] my 30s and had this really painful rash on the back of my head. [00:18] And when you're older and you get the shingles, [00:21] it tends to be even worse than that. [00:23] But there's this new study out about shingles. [00:25] That's pretty exciting. [00:26] Yeah. Basically what it it was looking at was whether or not [00:29] the shingles vaccine could lower the risk of dementia. [00:33] And the reason why they looked at it, [00:34] there is this theory out there that the cause of dementia might in part relate [00:39] to the virus that causes shingles and early in childhood causes chickenpox. [00:45] The problem is, studying that question is really hard because you need a lot of people. [00:49] Maybe, you know, tens of thousands of people who you randomized to get [00:53] the vaccine and not get the vaccine and then follow them over many years. [00:57] And that is a really hard thing to do. [00:59] So these guys came up with this really clever way to get at this question. [01:02] Yeah. The idea was that they took advantage of what you and I talk about all the time, [01:08] which is a natural experiment. [01:09] And that's where patients get randomized towards going down one path or another, [01:14] not because a researcher tells them to, [01:17] but just by accident. [01:19] In Wales about ten years ago, [01:21] they said that anybody born after a certain date in [01:24] 1933 was eligible for the shingles vaccine, [01:28] and anyone born before that date was not eligible for the shingles vaccine. [01:34] And since those people are all roughly the same age, [01:36] that line in the sand randomized them to either getting the shingles vaccine or not. [01:41] These authors estimate that getting the vaccine [01:44] by chance reduced the risk of dementia by about 20%, [01:47] and they had these few different mechanisms that they looked at. [01:50] But I think the ones where they think there might be some headway is one. [01:55] The vaccine itself just has some immune effect, right? [01:59] When you get a vaccine, [02:00] it stimulates the immune system in this robust way, [02:04] and that immune response might protect against dementia. [02:07] And the second relates to the actual virus itself. [02:10] If the virus in a reactivated form helps causes dementia, [02:15] then preventing reactivation might reduce the risk of dementia. [02:20] So those are the two mechanisms that they found some evidence for. [02:23] Still not completely clear, [02:25] but really interesting work. [02:27] And you know, we already knew that [02:29] the shingles vaccine helps reduce the risk of shingles, [02:32] which is really unpleasant. [02:34] And now there's this potentially added benefit of protecting against dementia. [02:39] What's a shame is that there's huge numbers of people who are, you know, [02:42] eligible and meet criteria to get the shingles vaccine, yet they don't. 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