Could an annual flu shot do more than protect against influenza? Researchers are exploring a possible link between flu vaccination and a lower risk of Alzheimer's disease. Times Now looked at what the evidence actually shows on 13 October 2026, with expert input from Dr. Arun Kumar, Senior Consultant Psychiatrist at Cadabam's Hospitals.
Where the 40% figure comes from
A 2022 study in the Journal of Alzheimer's Disease found that adults aged 65 and older who received at least one flu vaccine were about 40% less likely to develop Alzheimer's disease over four years than unvaccinated adults. The researchers compared 9,35,887 vaccinated adults with an equal number of unvaccinated adults.
The study was observational, though. It found an association between vaccination and lower Alzheimer's risk, but it could not show that the vaccine itself prevented the disease.
"The possibility that influenza vaccination may offer benefits for long-term brain health is an interesting development, but the findings need to be interpreted carefully," Dr. Kumar told the publication.
How a flu shot could affect the brain
One explanation under study is inflammation. Influenza can trigger a strong immune response, and severe infections can cause delirium or worsen cognitive difficulties in vulnerable older adults.
"Researchers are investigating whether preventing infections could reduce some of the inflammatory stress associated with cognitive decline," Dr. Kumar explained. The exact mechanism behind the possible connection has not yet been established.
The evidence is not conclusive
A 2025 systematic review and meta-analysis in Age and Ageing, covering eight studies and nearly 10 million people, found no statistically significant reduction in dementia risk across the general population. Lower risk was seen only in certain groups with underlying health conditions. Differences in lifestyle, overall health and access to healthcare between people who get vaccinated and people who don't may also shape the results.
"We should therefore not interpret the 40% figure as a guarantee that getting a flu shot will prevent Alzheimer's disease," Dr. Kumar cautioned.
What older adults can do
The flu vaccine remains important for reducing the risk of influenza and its serious complications. Its role in dementia prevention still needs more research. In the meantime, older adults can support brain health through regular physical activity, good sleep, social engagement and mental stimulation, and by keeping conditions such as hypertension and diabetes under control. Read more about whether dementia can be prevented.
"Vaccination may eventually prove to have additional benefits for cognitive health, but more research is needed before it can be recommended specifically as a dementia prevention strategy," Dr. Kumar said.
If you're noticing memory changes in yourself or a loved one, Cadabam's Hospitals' psychiatrists and geriatric care team can help. Call +91 97414 76476 for a confidential consultation.