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BEYOND INFECTION PREVENTION: THE SURPRISING BRAIN BENEFITS OF
VACCINES  
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Jess Steier and Sarah Scheinman
April 22, 2025
Unbiased Science
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_ New research suggests routine immunizations may help reduce
dementia risk _

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_Have you ever wondered if those routine shots at your doctor's office
could be doing more than just preventing the flu or shingles?_

Vaccinations are essential not only for training the immune system to
recognize and fight off harmful viruses and bacteria, but emerging
research suggests they may also play a surprising role in reducing the
risk of dementia. Dementia—one of the most pressing health
challenges in our aging population—affects over 57 million people
globally, with nearly 10 million new cases each year, according to
the World Health Organization
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It's currently the 7th leading cause of death worldwide and a major
contributor to disability and dependence among older adults.

Characterized by a decline in memory, thinking, and everyday
functioning, dementia has no known cure, but scientists continue to
explore strategies to reduce risk. Most prevention efforts focus
on healthy lifestyle habits
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as regular physical activity, balanced nutrition, managing blood
pressure and blood sugar, staying mentally active, and avoiding
smoking and excessive alcohol use. Now, another potential protective
factor has entered the conversation: VACCINES. _Let’s discuss!_

VACCINES? FOR BRAIN HEALTH?

At first glance, it may sound surprising. Vaccines are designed to
protect us from viruses like INFLUENZA, SHINGLES, PNEUMONIA,
and COVID-19, not cognitive decline. But large-scale studies suggest
that vaccines might also offer protective effects
against ALZHEIMER’S DISEASE, the most common form of dementia.

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A 2023  [[link removed]]study
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the _Journal of Alzheimer’s Disease_ analyzed health data from
nearly 2 MILLION U.S. ADULTS over 65. Those who received at least
one flu shot were 40% LESS LIKELY to develop Alzheimer’s over the
next four years.

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TETANUS, DIPHTHERIA, AND PERTUSSIS (TDAP) vaccines were linked to a 
[[link removed]]30%
LOWER RISK
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Alzheimer’s.

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PNEUMOCOCCAL VACCINES, often given to prevent pneumonia, were
associated with a 
[[link removed]]27%
REDUCED RISK
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A recent _Nature_ study
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people vaccinated against SHINGLES had a 20% LOWER CHANCE of
developing dementia over the next seven years.

These studies rely on large healthcare databases and follow people
over time, revealing associations between vaccination and reduced
dementia risk that are hard to ignore.

HOW COULD VACCINES AFFECT THE BRAIN?

While the evidence is compelling, scientists are still working to
understand HOW vaccines might help protect against dementia.

Here are some leading theories
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FEWER INFECTIONS, LESS INFLAMMATION: Many infections—especially in
older adults—can trigger systemic and brain inflammation, which is
known to contribute to neurodegeneration. Vaccines help prevent these
infections.

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IMMUNE SYSTEM TRAINING: Some vaccines may "train" the innate immune
system, improving its ability to clear toxic proteins
(like AMYLOID-Β) and regulate inflammation—both key factors in
Alzheimer’s disease.

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REDUCED COLLATERAL DAMAGE: Vaccines may help steer the immune
response away from harmful, chronic inflammation that can damage
healthy brain tissue.

That said, most of the current research is OBSERVATIONAL —meaning
we can't say for sure that vaccines _cause_ the reduced dementia
risk. Other factors, like the so-called HEALTHY-USER BIAS, may be at
play. People who get vaccinated may also be more health-conscious in
general, which itself lowers dementia risk.

STILL, THE EVIDENCE IS GROWING

Despite these limitations, the trend is consistent: multiple studies
across different vaccines and populations suggest that ROUTINE
IMMUNIZATIONS ARE ASSOCIATED WITH A LOWER RISK OF DEMENTIA.

Even if we’re still learning exactly why this is happening, the
implications are significant. Vaccines are widely available, already
part of public health recommendations, and—unlike some emerging
Alzheimer’s treatments—DON’T REQUIRE COSTLY INFUSIONS OR
SPECIALTY CLINICS.

RECENT BREAKTHROUGH: A NATURAL EXPERIMENT ON SHINGLES VACCINATION

A compelling 2025 study published in _Nature_ used a unique "natural
experiment" approach to establish a causal link between shingles
vaccination and reduced dementia risk, as analyzed by Dr. Jenn Dowd in
her "Data for Health" newsletter
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Dr. Dowd explains that researchers took advantage of a policy in Wales
that made the shingles vaccine available only to people born after
September 2, 1933, creating nearly identical comparison groups that
differed only in vaccine access. After following participants for
seven years, they found that those eligible for the shingles vaccine
had a 20% lower risk of developing dementia—but interestingly, this
benefit was observed only in women, not men. The study performed
numerous checks to strengthen the causation claim, including
confirming no pre-vaccine differences in dementia diagnosis and no
differences in unrelated health outcomes between groups. Additional
research found that the newer Shingrix vaccine (which has replaced the
older Zostavax used in the original study) may provide similar
protective benefits, suggesting that the mechanism likely involves
suppressing viral reactivation and modulating immune responses. This
research represents some of the strongest evidence to date for
vaccines as a potential dementia prevention strategy.

LOOKING AHEAD

More research is needed to confirm these findings and uncover the
mechanisms behind them. Important questions remain:

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Do repeated vaccinations (like annual flu shots) offer cumulative
brain benefits?

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Do different vaccine types (e.g., high-dose vs. standard flu shots)
vary in their effects?

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How do individual factors—such as age, genetics, or pre-existing
health conditions—shape vaccine-related brain outcomes?

While science continues to explore this fascinating connection, one
thing is becoming clear: those routine trips to the doctor for
vaccinations may be more valuable than we ever realized. As we
navigate an aging society where dementia threatens to affect more of
our loved ones each year, these accessible and affordable preventive
measures offer hope. They're already recommended for their proven
benefits against infectious diseases—the potential brain protection
is a powerful bonus. Whether you're due for your annual flu shot,
first-time shingles vaccine, or any other recommended immunization,
consider it an investment in your total health, brain included. After
all, when it comes to brain health, every little bit helps.

_Have you received your recommended vaccines this year?_

Stay Curious,

Unbiased Science

P.S. Want to support this kind of analysis? The best way is to
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for considering it!

_Dr. Jess Steier is a public health scientist, host of Unbiased
Science, and quirky and empathetic science communicator._

_Dr. Sarah Steinman is a neuroscientist, biomedical researcher and
co-host of the Unbiased Science podcast_

_Unbiased Science takes the time to explain complex topics with
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science._

* Science
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* vaccines
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* alzheimer's
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