Prime Highlights
- Research indicates that adult vaccines could reduce the risk of dementia by preventing viral infections that trigger brain inflammation and neuronal damage.
- Observational studies in Wales, Canada, and Australia found that vaccinated adults were less likely to develop dementia or experience it later than unvaccinated adults.
Key Facts
- The 2025 Wales study analyzed health records after the shingles vaccine rollout and used an age-based eligibility cutoff to compare similar groups.
- Vaccines like influenza, pneumococcal, hepatitis, and shingles remain underutilized among adults, even though they could offer potential long-term brain benefits.
Background
New research suggests that vaccines for adults may lower the risk of dementia because they protect people from viral infections and support long-term brain health. A recent perspective published in PLOS Biology highlights growing evidence that some vaccines could lower the chances of age-related neurodegenerative disease.
Scientists say certain viruses can cause brain inflammation, harm neurons, and raise the risk of conditions like Alzheimer’s disease. Researchers focus especially on herpes viruses, which may boost harmful protein buildup and trigger strong immune reactions in the brain. Vaccines may prevent initial infection and reduce later viral reactivation, which could limit this damage.
A large observational study published in Nature in 2025 analysed health records from Wales after the rollout of the shingles vaccine. Researchers found that vaccinated adults were much less likely to develop dementia than similar adults who were not vaccinated. The study used an age-based eligibility cutoff, which helped them compare similar groups of people and made their analysis stronger.
Follow-up studies in Canada and Australia found similar results. Researchers saw that people who got the herpes zoster vaccine developed dementia later or less often. Scientists warn that these results show only a connection, not proof that the vaccine directly prevents dementia. Differences in lifestyle, diet, and physical activity between vaccinated and unvaccinated groups may influence results.
Experts say the biological mechanism remains unclear. Vaccines may work indirectly by preventing infections that harm the brain or by training the immune system to respond more effectively. More targeted clinical trials will be required to confirm these effects.
Public health specialists say the findings could be important for ageing countries such as India, where the elderly population is rising quickly and dementia cases already affect millions. Adult vaccination coverage remains low and is not fully integrated into routine healthcare, despite the availability of vaccines for influenza, pneumococcal disease, hepatitis, and shingles.
Researchers call the potential brain benefit an “off-target effect,” meaning it goes beyond the vaccine’s main goal of preventing infection. Right now, regulators approve vaccines based on their main results, but future trials could directly test if they lower the risk of dementia.
