Eight vaccines linked to a lower risk of dementia
A growing body of research is beginning to reveal the impact that regular routine vaccines could be having on the likelihood of conditions like dementia. Here are the jabs with the strongest evidence so far.
- 28 April 2026
- 8 min read
- by Priya Joi
At a glance
- Multiple large observational studies have found that routine adult vaccines are associated with a reduced risk of dementia, with some showing risk reductions of 25% to 40%.
- The strongest evidence exists for shingles, flu, RSV, pneumococcal and diphtheria, tetanus and pertussis-containing (DTP) vaccines.
- Researchers believe vaccination may reduce dementia risk by preventing infections that cause brain inflammation, though some evidence points to a more general immune effect.
More than 57 million people worldwide are living with dementia and, according to the World Health Organization, there are 10 million new cases every single year.
But over the past few years, a striking pattern has emerged from large population studies: vaccinations can be protective against dementia. The effect has now been observed across multiple vaccines, multiple countries and millions of people.
Viral infections can trigger long-lasting inflammation in the body, which then extends to the brain. That inflammation can damage the ability of brain cells to communicate with each other which, in turn, can lead to cognitive impairment and memory loss, leading to dementia.
The rationale behind vaccines protecting neurodegenerative diseases like dementia and Alzheimer’s comes from the way that viral infections can affect our brain.
Dementia is not a single disease, but a term for a cluster of symptoms, including memory loss and cognitive decline, that can have many causes. Alzheimer’s disease is the most common of those causes, accounting for an estimated 60-70% of cases.
Several viruses including herpes simplex virus type 1 (that causes cold sores), chickenpox virus (varicella zoster virus that also causes shingles) and SARS-CoV-2 (which causes COVID-19) have all been linked to a higher risk of Alzheimer’s disease and dementia after infection.
Viral infections can trigger long-lasting inflammation in the body, which then extends to the brain. That inflammation can damage the ability of brain cells to communicate with each other which, in turn, can lead to cognitive impairment and memory loss, leading to dementia.
Here are eight vaccines that have been shown to have a protective effect against dementia.
1. Shingles
The shingles vaccine has the most replicated evidence of any vaccine for dementia risk reduction.
A 2024 study in Nature Medicine found that the recombinant shingles vaccine Shingrix was associated with a significantly lower risk of dementia than the older live vaccine Zostavax, which has since been discontinued in the USA.
A key difference between the two is that Shingrix contains an ingredient called AS01, an adjuvant designed to boost the immune response.
A follow-up study from the same group, published in NPJ Vaccines in 2025, tracked more than 436,000 people and found an 18% reduction in dementia diagnoses over 18 months in those who received the shingles vaccine.
2. RSV
The respiratory syncytial virus (RSV) vaccine is a relatively new addition to adult immunisation schedules, but it has already been linked to dementia protection.
The Oxford NPJ Vaccines study found a 29% reduction in dementia risk over 18 months in those who received the RSV vaccine, Arexvy.
What makes this finding particularly interesting is that Arexvy contains the same AS01 adjuvant as the shingles vaccine, Shingrix. The fact that both vaccines showed similar levels of protection, despite targeting completely different viruses, led the researchers to suggest that the adjuvant itself may play a direct role in lowering dementia risk.
3. Flu
Flu vaccination has been studied more extensively than any other vaccine in relation to dementia.
A 2022 study published in the Journal of Alzheimer’s Disease analysed nearly two million people aged 65 and older and found that those who received at least one flu vaccine were 40% less likely to develop Alzheimer’s over four years. The more frequently people were vaccinated, the greater the protection.
In April 2026, the same team published new findings in Neurology showing that a high-dose flu vaccine, which contains four times the antigen of the standard jab, was linked to a 55% reduced risk.
That finding comes from a single retrospective study and will need replication, but it adds to a consistent body of evidence around influenza vaccination and cognitive protection.
4. DTP (diphtheria, tetanus and pertussis)
A 2023 study in the Journal of Alzheimer’s Disease found that adults aged 65 and over who received the tetanus, diphtheria and pertussis (Tdap) or Td (without pertussis) vaccine were 30% less likely to develop Alzheimer’s over an eight-year follow-up.
A meta-analysis in Frontiers in Immunology, pooling data from 17 studies and more than 1.8 million people, had uncovered a similar finding in 2022: the risk of developing dementia was reduced by 31%.
A more recent meta-analysis in Age and Ageing (2025), covering 104 million participants, confirmed the association, showing a 33% reduction.
DTP is one of the most widely administered vaccines in the world, so even a modest protective effect against dementia would have enormous public health implications.
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5. Pneumococcal
The same 2023 study found a 27% reduced risk of Alzheimer’s in adults who had received the pneumococcal vaccine.
A 2025 Age and Ageing meta-analysis, which pooled data from 21 studies covering 104 million participants, also found a significant association.
Fewer independent studies have examined pneumococcal vaccination than shingles or flu, but the consistency of the finding across both a large cohort and a major meta-analysis suggests the association is worth investigating further.
6. Hepatitis A
Hepatitis A vaccination was among the vaccines identified in the Cambridge review as protective.
The Frontiers in Immunologymeta-analysis indicated a 22% lower risk of dementia. A systematic review from the University of Cambridge in January 2025 analysed 14 studies drawing on health records from roughly 130 million people.
Among its findings, vaccinations against hepatitis A, typhoid and the combined hepatitis A and typhoid vaccine were all associated with a lower risk of dementia.
A Welsh population study by Wilkinson and colleagues, published in the Journal of Epidemiology and Community Health, found that receiving both the typhoid and hepatitis A vaccines together was associated with a greater reduction in risk than either vaccine on its own.
That pattern, where combining vaccines appears to offer more protection, shows up repeatedly across the research.
7. Hepatitis B
Hepatitis B vaccination appeared in the same Frontiers in Immunology meta-analysis, with a hazard ratio of 0.82, indicating an 18% lower risk of dementia.
The Cambridge systematic review also flagged the combined hepatitis A and B vaccine as showing a greater protective effect than either alone.
This is consistent with a broader pattern in the literature where receiving multiple different vaccinations appears to be associated with a lower risk than receiving just one, though researchers caution that this could also reflect the healthy vaccinee effect rather than a biological mechanism.
8. Typhoid
Typhoid vaccination was linked to a 20% reduced risk of dementia in the Frontiers in Immunology meta-analysis and in the Cambridge systematic review.
The original data on typhoid came from the Welsh population study by Wilkinson and colleagues, which examined the association between all prescription medications and dementia incidence across more than half a million people. Of 744 medications analysed, only four were associated with a lower risk of dementia, and all four were vaccines.
These are not vaccines that most adults receive as part of their standard immunisation schedule. But the fact that they show a similar pattern to the five routine vaccines above is notable and adds weight to the idea that the protective effect may not be specific to any single pathogen.
Why might vaccines protect the brain?
Researchers are still working to untangle the mechanisms, and there are several theories that are not mutually exclusive.
The most straightforward is that vaccines prevent infections, and infections cause inflammation that can damage the brain.
A Korean nationwide cohort study published in Alzheimer’s Research & Therapy in 2024 found that both herpes simplex and varicella zoster virus infections were independently associated with an increased risk of dementia, with a particularly elevated risk in people who experienced both.
An Italian population study of more than 130,000 people, published in The Journal of Prevention of Alzheimer’s Disease in 2025, found a 13% increased risk of dementia following severe shingles.
And a 2025 study in Nature Medicine led by researchers at Imperial College London and the UK Dementia Research Institute found that people who had previously contracted COVID-19 showed increased levels of blood biomarkers linked to amyloid build-up in the brain, which is linked to Alzheimer’s disease, with effects comparable to four years of ageing.
By stopping or reducing the severity of these infections, vaccines may be preventing the neuro-inflammation that contributes to cognitive decline.
A second theory focuses on what some researchers call non-specific effects of vaccination: the idea that vaccines can have broader effects on the immune system beyond protection against a single pathogen.
The Oxford finding that the AS01 adjuvant may itself reduce dementia risk supports this. The NPJ Vaccines study notes that AS01 activates macrophages and dendritic cells and triggers the production of interferon gamma, a molecule that has been shown in mouse models to reduce amyloid plaque deposits.
Whether this mechanism translates to humans is not yet established. A 2026 review in Frontiers in Immunology proposed a broader immunological model for how vaccines might protect against dementia, drawing on evidence from AS01 vaccines, BCG and other immunisations.
A third possibility is the healthy vaccinee effect: people who get vaccinated might be more likely overall to look after their health, and that broader health advantage may explain at least part of the observed risk reduction.
This remains the most important caveat. Most studies adjust for this, and several have found that the association persists after controlling for income, comorbidities and other health behaviours.
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