Memory Digest

Vaccines, Infections and Dementia Risk

Strong natural-experiment studies suggest the shingles vaccine may lower the risk of dementia; learn what the research shows, how infections might affect the brain, and what it means for you.

Last reviewed: October 2026

Could a vaccine lower your chance of dementia? A few years ago, that sounded far-fetched. Now some of the most convincing evidence in dementia prevention points to the shingles vaccine. Here's what's known, and what isn't.

Why infections might matter

Shingles is caused by the same virus as chickenpox (varicella-zoster). After chickenpox, the virus hides in nerve cells for life and can reawaken decades later as a painful rash. Other herpes viruses, such as the cold-sore virus (herpes simplex 1), also live quietly in the nervous system.

Scientists have several ideas about how infections might affect dementia risk:

• Viruses that reawaken may trigger inflammation in the brain (see Inflammation and the Brain).
• Some lab studies suggest amyloid may act partly as a defense against microbes, so infections could encourage plaque buildup.
• Serious infections and hospital stays can cause delirium, which is linked to faster decline afterward (see Delirium vs. Dementia and Hospital Stays and Dementia).
• Vaccines may also have broader "off-target" effects that strengthen the immune system.

None of these ideas is proven. But the vaccine studies are hard to ignore.

The Wales shingles study

In Wales, the shingles vaccine program that began in 2013 had a strict birthday cutoff. People born on or after September 2, 1933 became eligible. People born even a week earlier were never eligible. That created a rare "natural experiment": two groups of people almost identical in every way except their access to the vaccine.

Researchers led by Pascal Geldsetzer at Stanford used health records to follow these groups. In their 2025 study in Nature, getting the vaccine (an older, live version called Zostavax) lowered the chance of a new dementia diagnosis over seven years by about 20% compared with similar people who didn't get it. The effect appeared stronger in women than in men.

Because the cutoff was essentially random, this design gets closer to proving cause and effect than typical observational studies, which can be skewed by the fact that people who get vaccines tend to be healthier in other ways.

More results since

• Other countries. The same team found similar signs in Australia, which also used a birthdate cutoff.
• A follow-up in Cell (2025). Using the Welsh data again, the researchers found the vaccine also reduced diagnoses of mild cognitive impairment, and among people who already had dementia, fewer died from dementia. The benefit didn't seem limited to one type of dementia.
• Newer vaccine. Most people today get Shingrix, a non-live vaccine that is more effective at preventing shingles. Several large observational studies have linked Shingrix to a lower dementia risk than the older vaccine or no vaccine, but it hasn't been tested with the same kind of natural experiment yet.

What it means for you

• The shingles vaccine is already recommended to prevent shingles, which can be very painful and can cause long-lasting nerve pain. The CDC recommends two doses of Shingrix for adults 50 and older, and for adults 19 and older with weakened immune systems.
• A possible lower dementia risk is a bonus, not a proven guarantee. No vaccine is approved to prevent dementia.
• Ask your doctor or pharmacist whether you're due. In the U.S., Shingrix is covered at no cost under Medicare Part D and most private insurance plans. Your pharmacist can check.

Other vaccines and infections

• Other vaccines, such as flu and pneumonia shots, have been linked to lower dementia risk in observational studies. These findings are less certain, but the vaccines are worth getting for their own sake.
• Treating infections promptly, especially urinary infections and pneumonia in older adults, can prevent delirium and hospital stays.
• Gum disease has also been linked to dementia, possibly through inflammation. Good dental care is a sensible habit.

The bottom line

The shingles vaccine has some of the strongest evidence of any single step that might lower dementia risk. It's already recommended for adults 50 and older, so if you haven't had it, it's worth a conversation with your doctor or pharmacist.

This article is for general information and is not a substitute for advice from your own doctor.

Sources

1. Eyting M et al. A natural experiment on the effect of herpes zoster vaccination on dementia. Nature, 2025
2. Xie M et al. The effect of shingles vaccination at different stages of the dementia disease course. Cell, 2025
3. Centers for Disease Control and Prevention: Shingles Vaccination

Not medical advice. This article is general information, not a diagnosis or treatment plan for any individual. Talk with a doctor about your situation.

Related articles

• Inflammation and the Brain
• Reducing Dementia Risk: The 14 Risk Factors
• Dementia Research Today
• Delirium vs. Dementia
• Hospital Stays and Dementia