Routine vaccines could prevent dementia – here's how
Viruses can cause damage to the brain, which is why evidence is emerging that vaccines against illnesses like diphtheria or flu could help protect against neurological diseases like Alzheimer’s.
- 6 February 2025
- 4 min read
- by Priya Joi
Vaccines against diseases as varied as diphtheria and hepatitis could help prevent dementia later in life, according to a new study of over 130 million people.
The study suggests that antivirals and routine vaccines have a broader impact on the immune system, lessening the risk of dementia.
The research also bolsters studies indicating that dementia could be partly attributable to infection with viral or bacterial pathogens.
This shows that, as well as protecting lives in the short term, vaccines could have critical long-term benefits for our immune system.
The 130 million people study
In a study published last month, Benjamin Underwood at Cambridge University, UK, and colleagues analysed health data from 130 million people, which included 1 million people who had been diagnosed with dementia.
They found that four vaccines were associated with a lowered risk of dementia: hepatitis A, typhoid, combined hepatitis A and typhoid vaccine, and diphtheria. They also noted that antibiotics, antivirals and anti-inflammatory drugs were all associated with reduced dementia risk.
The study builds on research from 2023 in the Journal of Alzheimer’s Disease, showing that those who got the diphtheria vaccine were 30% less likely to get Alzheimer’s disease (the leading cause of dementia) compared to those who did not get the vaccine.
The risk of Alzheimer’s was 25% lower with shingles vaccination, and 27% lower with pneumococcal vaccination. The same researchers had previously shown that people who had taken the influenza vaccine were 40% less likely to develop Alzheimer’s.
Viral infections can threaten the brain
Viruses have long been associated with neurodegenerative disease, and there is evidence that 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) all can lead to a higher risk of Alzheimer’s disease and dementia following infection.
Common infections like these can cause long-lasting inflammation in the body. The link with dementia comes when this inflammation extends to the brain. There it can trigger chemicals that damage brain cells and their ability to communicate with one another.
This can lead to cognitive impairment and memory loss, paving the way for dementia. Preventing and reducing the severity of viral or bacterial infections with immunisation should therefore reduce the amount of brain inflammation a person experiences.
A 2023 study in Frontiers in Pharmacologystatedthat infection with the influenza A virus could result in the loss of dendritic spines – an integral part of the nervous system – impair the strengthening of synapses in the hippocampus and cause deficits in spatial memory formation. According to the authors, “vaccination might indeed provide the best strategy to prevent these neuropathological alterations.”
Significant cognitive impairment has also been seen in people with Long COVID. Research published in January 2025 led by researchers at Imperial College London and the UK Dementia Research Institute showed that people who had previously had COVID-19 were more likely to have increased levels of biomarkers linked to faulty amyloid proteins in the brain – a build-up of amyloid proteins is a signature of Alzheimer’s disease. The scientists say that even mild or moderate COVID-19 may speed up biological processes that lead to the build-up of amyloid proteins in the brain.
A 2022 study found that people over 65 years who had COVID-19 had a nearly 70% increased risk of getting diagnosed with Alzheimer’s within a year.
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So how might vaccines protect against dementia?
By preventing infections – or limiting their severity – vaccines can stop the resulting neuroinflammation that could lead to cognitive impairment.
This ties in with Underwood et al’s finding of a link between the use of anti-inflammatory medications and a reduced risk of dementia. Most notably this includes non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, which they argue could potentially protect against memory decline.
What’s clear is that as well as a protective effect from childhood vaccines against diphtheria, for example, immunisation against diseases such as influenza and COVID-19 in adults could be important in preventing dementia.
