An unexpected idea is emerging in medicine: vaccines may protect not only against infections, but also against dementia.
The evidence is strongest for the shingles vaccine. Originally designed to prevent a painful blistering rash caused by shingles (herpes zoster), it may also lower the risk of dementia by as much as 20%.
“They’ll protect against these really potentially severe infections, especially in older adults, and preventing that alone is huge,” said Dr. Avram Bukhbinder, a resident physician at Massachusetts General Hospital who has studied vaccines and dementia risk.
“There seems to also be some kind of added benefit and ultimately it just adds a more compelling reason,” he added, referring to the lower rates of dementia seen in people who’ve received shots for shingles, flu, RSV, and Tdap.
For a neurodegenerative disease with no cure and few treatments, this is no small claim.
From Shingles and Beyond
Dementia affects about nine million people in the U.S., and the number is expected to double by 2060. It robs people of memory, independence, and the ability to recognize those they love. Families face enormous emotional and financial burdens.
It goes without saying that an effective preventive measure could change lives.
That is why researchers have been combing through large health databases and running natural experiments. The shingles vaccine, first introduced in 2006, quickly became a candidate of interest. A Nature study in 2025 tracked nearly 300,000 older adults in Wales. Because eligibility for the vaccine depended on date of birth, researchers could compare two groups of people born just weeks apart. Over seven years, those who received the vaccine were 3.5% less likely to develop dementia. That’s about a 20% relative risk reduction.
The newer recombinant shingles vaccine, Shingrix, is especially effective and now standard in the United States. The CDC recommends two doses for adults 50 and older, or younger adults with weakened immune systems. Still, as of 2022, only about a third of eligible Americans had received even one dose.
Other studies came to similar conclusions. A U.S. study of more than 200,000 older adults found lower dementia risk in both recipients of the older live vaccine (Zostavax) and the newer recombinant vaccine (Shingrix). The benefit was greater for Shingrix, which gave people an average of 164 more dementia-free days compared with Zostavax.
The trend is not limited to shingles.
The Growing Case for Vaccines Offering Protection Against Dementia
Tdap protects against tetanus, diphtheria, and pertussis (whooping cough). Unlike shingles or RSV, its role in dementia is less obvious. But evidence is mounting. A 2022 Journal of the American Geriatrics Society study found that people who received both the shingles and Tdap vaccines had a 50% lower risk of developing dementia than those who received no vaccines. The CDC recommends a Tdap booster for adults every 10 years, yet in 2022, only about 30% of adults ages 19–64 had received it.
A flu vaccine study covering 1.8 million Americans over age 65 reported a 40% lower risk of Alzheimer’s disease in vaccinated individuals. A separate 2024 study of more than 70,000 people found a 17% reduction in dementia risk among those who got the vaccine. Yet fewer than half of Americans get their flu shot each season, despite CDC recommendations that everyone over six months old should be vaccinated.
And the new RSV vaccine, given mostly to people over 60, has shown similar effects. A team at Oxford reported that Arexvy, an RSV vaccine, was linked to a 29% reduction in dementia diagnoses in the 18 months following vaccination.
“Our findings show that vaccines against two separate viruses, shingles and RSV, both lead to reductions in dementia,” said Associate Professor Maxime Taquet of Oxford University in npj Vaccines. “This gives another reason to have the vaccines, in addition to their effectiveness at preventing these serious illnesses.”
Respiratory syncytial virus (RSV) often causes mild cold-like symptoms but can be deadly in infants and older adults. Each year, RSV is linked to 100–300 deaths in U.S. children under 5 and 6,000–10,000 deaths in people over 65. The CDC now recommends the RSV vaccine for adults 75 and older, and for people over 50 at higher risk.
Why Might This Be Happening?
Scientists are cautious. Most of these studies are observational, so they show correlations, not proof of cause and effect. Still, explanations are beginning to take shape.
First, preventing infection itself may matter. Severe illnesses like flu, shingles, and RSV are known to accelerate brain aging. A 2024 study in Nature Aging showed that such infections can trigger inflammation, leading to faster brain atrophy and higher dementia risk later in life.
Second, the vaccines may be doing something more than just stopping disease. The newer shingles vaccine (Shingrix) and the RSV vaccine (Arexvy) both contain an adjuvant, AS01, that stimulates the immune system. Laboratory studies suggest that AS01 activates immune cells that may help protect the brain from damage. “We need studies to confirm whether the adjuvant present in some vaccines contributes to the reduced dementia risk, and to understand how it does so,” said Professor Paul Harrison of Oxford.
A third possibility involves stroke risk. Shingles has been linked to higher rates of stroke, which itself is a major driver of dementia. Preventing shingles may therefore indirectly lower dementia cases.
Curiously, some studies have found the protective effect stronger in women than men, though why this happens is unclear.
The idea that a vaccine could help shield the brain from dementia is extraordinary. In medicine, side effects are usually unwanted. Here, researchers may have stumbled upon a rare kind of side effect — one that could change the trajectory of aging.
For now, the advice from experts is practical: get vaccinated if you are eligible. “Until then, get your shingles vaccination if you’re eligible for it. It can prevent painful episodes of shingles — and may do much more,” wrote Dr. Robert H. Shmerling in an article for Harvard Health Publishing.
Vaccines are no magic bullet, though. They work best alongside other preventive measures. The 2024 Lancet Commission estimated that up to 45% of dementia cases could be delayed or prevented through lifestyle and environmental changes: staying physically active, moderating alcohol, controlling blood pressure, and treating hearing loss.
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