Could the shingles vaccine already lower dementia risk?

Scientists do not yet have an approved vaccine specifically designed to prevent dementia. But one vaccine already widely used by older Americans has produced surprisingly encouraging results: the shingles vaccine.

Several large studies have found that people receiving shingles vaccination subsequently developed dementia less often than comparison groups. The evidence is intriguing enough that researchers are now trying to determine whether the effect is real — and, if so, why.

What the studies found

Zostavax: A 2025 Nature study examined an unusual vaccination program in Wales in which eligibility for the older shingles vaccine depended almost entirely on a person's exact birth date.

That created what researchers called a "natural experiment": otherwise similar people on opposite sides of the eligibility cutoff had dramatically different vaccination rates.

Over seven years, receiving the vaccine was associated with about a 20% reduction in the probability of being diagnosed with dementia, according to Nature.

The effect appeared particularly strong among women.

Shingrix: Zostavax is no longer used in the United States. It has been replaced by Shingrix, the two-dose recombinant shingles vaccine now recommended for most adults 50 and older.

A 2024 Nature Medicine study compared more than 200,000 people vaccinated during the transition from Zostavax to Shingrix. People receiving the newer vaccine experienced 17% more time without a dementia diagnosis over the following six years, equivalent to about 164 additional dementia-free days among people who eventually developed the disease.

The association appeared in both men and women, although it was stronger among women. Researchers emphasized that the study was observational and therefore could not prove that Shingrix itself prevented dementia.

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It may not be just about shingles

There is another intriguing clue.

Shingrix contains an immune-system stimulant called AS01. The same type of adjuvant is used in an RSV vaccine.

Researchers studying health records from more than 436,000 people found that both AS01-containing shingles and RSV vaccines were associated with reduced dementia risk during an 18-month follow-up period. That raises the possibility that the immune response generated by the vaccine — rather than simply preventing shingles — could contribute to the apparent effect, another Nature report said.

Scientists are also investigating whether preventing reactivation of the varicella-zoster virus could reduce inflammation or neurological damage that contributes to dementia.

What this does not mean

For now, Shingrix is not an approved Alzheimer's or dementia-prevention treatment, and consumers should not assume that getting the vaccine will prevent dementia.

The studies are unusually compelling, particularly the Welsh natural experiment, but researchers still need randomized clinical trials and additional long-term evidence to establish whether the relationship is truly causal.

There is, however, already a well-established reason for eligible adults to consider Shingrix: it is designed to prevent shingles and its potentially serious complications.

If preventing dementia eventually turns out to be another benefit, it would be a remarkable bonus from a vaccine already sitting on pharmacy shelves.