A large 2026 study found that adults age 65 and older who received two doses of Shingrix had a much lower risk of dementia than unvaccinated adults. The findings are promising, but researchers say the vaccine is not yet proven to prevent Alzheimer’s.
Most people think of the Shingrix vaccine as a way to prevent shingles. That makes sense. Shingles can be very painful, and the vaccine was made to stop that problem. But now researchers are seeing something surprising. The same vaccine may also help lower the risk of dementia, including Alzheimer’s disease.
That is a big deal. Alzheimer’s disease is the most common cause of dementia, and millions of older adults are living with it. The Alzheimer’s Association says about 7.2 million Americans age 65 and older are living with Alzheimer’s in 2025. Earlier national estimates found about 6.9 million Americans age 65 and older were living with Alzheimer’s dementia in 2024.
A new 2026 study published in Nature Communications looked at whether the recombinant zoster vaccine, better known as Shingrix, was linked to a lower risk of dementia. The researchers studied Kaiser Permanente Southern California members age 65 and older. They compared 65,800 people who got two doses of Shingrix with 263,200 similar people who did not get the vaccine.
The results got a lot of attention. People who received two doses of Shingrix had a 51% lower risk of dementia than those who were unvaccinated. In the study, dementia happened in about 5.67% of the vaccinated group compared with 10.64% of the unvaccinated group during follow-up. The benefit appeared across age groups and racial and ethnic groups, and it was stronger in women than in men.
That sounds amazing, and it is very promising. But there is one important point: this study shows an association, not final proof that Shingrix directly prevents Alzheimer’s disease. In simple terms, the vaccine was linked with lower dementia risk, but the study was not a randomized trial designed to prove cause and effect.
The researchers knew that one big question would come up right away. What if people who get vaccines are already healthier, more careful, and more likely to see doctors? That is called “healthy vaccinee bias.” To test that, the team also compared Shingrix recipients with people who got a Tdap vaccine instead. Even then, the Shingrix group still had a lower dementia risk, with an adjusted hazard ratio of 0.73. That means the lower risk did not disappear after the researchers tried to account for that bias.
So why might this happen? Scientists do not know for sure yet. One idea is that preventing shingles may reduce harmful inflammation linked to the nervous system. Shingles happens when the chickenpox virus wakes back up later in life. Some researchers think that viral reactivation and inflammation may play a role in brain aging and dementia. Another idea is that the vaccine may stimulate the immune system in a way that helps protect the brain. Right now, those are still theories, not proven facts.
It is also important to keep expectations realistic. This does not mean Shingrix is a cure for Alzheimer’s. It also does not mean people should get the vaccine only to protect memory. At this point, Shingrix is officially recommended to prevent shingles, not to treat or prevent dementia. The CDC recommends Shingrix for adults age 50 and older, given as two doses, usually 2 to 6 months apart.
Still, these findings matter. Shingrix is already widely available. It is already recommended for many older adults. And if future studies confirm that it also helps protect the brain, that would be a huge bonus. Sometimes the biggest breakthroughs do not start with a brand-new drug. Sometimes they come from taking a fresh look at something we already have.
There are also a few limits to remember. The study followed people for a little over three years on average, which is not very long for a disease that develops slowly over time. The research was done in one large health system, so the results may not apply equally to every population. Even though the study was strong and carefully done, more research is still needed.
The bottom line is encouraging. A routine shingles vaccine may do more than prevent a painful rash. It may also help lower dementia risk in older adults. That is exciting news, especially because Alzheimer’s disease remains such a major problem for families everywhere. But for now, the best way to look at this study is with hope and caution at the same time: hope because the results are strong, and caution because more studies must confirm exactly what the vaccine is doing.
If you are age 50 or older and have not had Shingrix, this research gives you one more reason to talk with your doctor or pharmacist. The vaccine is already recommended to prevent shingles. Protecting your skin from a painful rash is good enough. Protecting your brain too would be even better.