A series of studies has found that the shingles vaccine may even prevent dementia. Following the United Kingdom, long-term cohort studies tracking hundreds of thousands of people in Canada, New Zealand, and Australia showed that the vaccine reduced not only shingles but also dementia by 20%. With no clear way to diagnose and treat dementia early, expectations are growing that the shingles vaccine could serve as a "second-best option" for preventing dementia.
A research team led by Pascal Geldsetzer of Stanford University School of Medicine said in Lancet Neurology on Feb. 6 that "in a follow-up study of more than 460,000 residents in Ontario, Canada, those eligible for the shingles vaccine had an absolute 2 percentage point lower rate of being diagnosed with dementia over five and a half years than others." Considering dementia incidence among people 65 and older, vaccination appears to reduce the risk of dementia by about 20% compared with previous levels.
◇ Dementia prevention effect confirmed through vaccine policy changes
Dementia is an acquired disorder in which degenerative brain diseases or cerebrovascular diseases reduce cognitive functions such as memory, language ability, and judgment, interfering with daily life. Two-thirds of dementia patients have Alzheimer's disease. Alzheimer's disease is a degenerative brain disorder in which abnormal accumulation of amyloid beta and tau proteins in the brain leads to the death of neurons.
Drugmakers have successively launched antibody therapies that clear amyloid beta proteins accumulated in the brain, but without a way to diagnose early, it has been difficult to see benefits. That is because treatments are effective only at the very early stage of onset. Prevention is best, but no vaccine has yet been developed.
The researchers proposed the shingles vaccine as an alternative. From Jan. 1, 2017, to June 30, 2022, 10,789 people were diagnosed with dementia in primary care practices in Ontario. The usual age criterion for free shingles vaccination in Ontario is 65 to 70. When the researchers examined dementia cases around this age range, those who received the shingles vaccine had about a 20% lower risk of a dementia diagnosis than the unvaccinated.
The fact that the shingles vaccine can prevent dementia was first confirmed in the United Kingdom. Geldsetzer's team published in Cell last year a seven-year follow-up of medical records for more than 280,000 older adults ages 71 to 88 in Wales who had never been diagnosed with dementia. Those who received the shingles shot had a 37% lower risk of developing shingles than the unvaccinated, and a 20% lower risk of a dementia diagnosis.
That finding emerged thanks to a vaccine shortage. When the shingles vaccine became scarce in September 2013, the Welsh government offered one year of free vaccination only to people turning 79 that year. Residents already 80 or older were excluded from vaccination. This created a "natural clinical trial" environment to observe the effect of the shingles vaccine on dementia onset independent of other factors. The researchers later confirmed the same results in Australia and New Zealand, and now in Canada.
◇ Inactivated vaccine is more effective than live vaccine at preventing dementia
Shingles is a neurological disease triggered when the varicella-zoster virus latent in the nervous system reactivates as immunity wanes. In childhood it manifests as chickenpox, causing blisters all over the body, but in adults, when the latent virus reactivates, shingles appears with band-like rashes on the skin and severe neuralgia.
Shingles vaccines on the market fall into two types: live attenuated vaccines and recombinant protein vaccines (inactivated). Live attenuated vaccines are made by weakening the virulence of the live varicella-zoster virus. Zostavax from Merck, the world's first shingles vaccine, and Sky Zoster from SK bioscience use this approach.
Recombinant vaccines are made by inserting varicella-zoster viral genes into Chinese hamster ovary (CHO) cells. The viral proteins produced by culturing and purifying the cells are injected into the body to induce an immune response. Shingrix from GSK plc, which currently dominates the market, uses this method.
The shingles vaccine confirmed to reduce dementia risk in Wales was Zostavax, a live vaccine from MSD. But Zostavax has relatively lower efficacy and diminished immune effects in the elderly, leading to supply discontinuation in several countries, including Korea. After Zostavax's withdrawal, Shingrix from GSK was found to be more effective not only against shingles but also in preventing dementia.
Researchers at the University of Oxford tracked the dementia prevention effects of the two vaccines for six years, taking advantage of the cessation of live vaccine use in the United Kingdom after Shingrix's approval. According to a paper published in 2024 in Nature Medicine, those who received Shingrix took six months longer to be diagnosed with dementia than those who received Zostavax. That indicates better preventive efficacy.
Of course, live vaccines still have advantages as shingles vaccines. Sky Zoster, developed in-house by SK bioscience, increased its market share after entering the market in 2017, benefiting from MSD's withdrawal of Zostavax. Shingrix requires two doses two months apart, but Sky Zoster is a single dose. The price is about one-third that of Shingrix. The company also said it causes fewer side effects such as arm pain and fever after injection.
◇ Also shows an effect in slowing aging
The additional benefits of the shingles vaccine are not limited to dementia. A team led by Kim Jeong-gi of the University of Southern California (USC) Leonard Davis School of Gerontology reported in The Journals of Gerontology: Series A in Jan. that the shingles vaccine showed an effect in slowing aging.
The researchers assessed 3,884 adults ages 70 and older, assigning a healthy aging score based on seven indicators including inflammation and time-dependent DNA effects. They concluded that those who had previously been vaccinated had markedly lower inflammation levels and higher overall healthy aging scores.
It is still unclear how the shingles vaccine prevents dementia and aging. Scientists suspect it prevents shingles and reduces neuroinflammation while strengthening the immune system. Because the shingles virus lies dormant in neurons, the vaccine may prevent nerve damage and protect cognitive function. Immune cells induced by the shingles vaccine could boost immunity and slow the pace of aging.
In many countries, free shingles vaccination is offered only to older adults. The Stanford team noted that more evidence is needed before recommending that younger people get the shingles shot to prevent dementia. Although policy shifts created natural clinical trials, rigorously designed clinical trials are required to determine precisely how long the dementia prevention effect lasts and which age groups benefit more.
Even so, Geldsetzer recommends getting the shingles vaccine. "Based on results from multiple countries, we estimate that 1 in 5 people newly diagnosed with dementia over seven years could be prevented by the shingles vaccine," he said. "I consider the evidence sufficient for me to get the shingles shot myself."
References
Lancet Neurology (2026), DOI: https://doi.org/10.1016/S1474-4422(25)00455-7
The Journals of Gerontology: Series A (2026), DOI: https://doi.org/10.1093/gerona/glag008
Cell (2025), DOI: https://doi.org/10.1016/j.cell.2025.11.007
Nature Medicine (2024), DOI: https://doi.org/10.1038/s41591-024-03201-5