Beyond Infection Prevention: The Surprising Brain Benefits of Vaccines
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. 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 such 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.
-
A 2023 study in 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.
-
Tetanus, diphtheria, and pertussis (Tdap) vaccines were linked to a 30% lower risk of Alzheimer’s.
-
Pneumococcal vaccines, often given to prevent pneumonia, were associated with a 27% reduced risk.
-
A recent Nature study found that 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:
-
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.
-
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.
-
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. 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:
-
Do repeated vaccinations (like annual flu shots) offer cumulative brain benefits?
-
Do different vaccine types (e.g., high-dose vs. standard flu shots) vary in their effects?
-
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 subscribe to our Substack and share our work. While all our articles are always completely free to read, paid subscriptions help sustain our in-depth reporting on vaccine policy and public health. Thank you 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 patience and evidence. Subscribe. If you value our approach to making science accessible to all, please consider upgrading to a paid subscription if you haven’t already. Your support helps us reach more people with trustworthy, empathetic science communication - no nonsense, just science.