Two Studies, 24 Hours Apart, Tie the Shingles Vaccine to Lower Dementia and Heart Disease

What each study actually found

The dementia study, led by researchers at Brown University and published in the Annals of Internal Medicine, followed 509,926 adults aged 66 and older admitted to more than 5,500 skilled nursing facilities between 2017 and 2022. Only 8,843 of them were vaccinated. Over four years, dementia was diagnosed in 18.8 percent of the vaccinated group versus 24.6 percent of the unvaccinated group, a 24 percent relative reduction the authors translate to roughly one dementia case potentially prevented per 17 people vaccinated.

The heart study took a different, cleverer approach. Rather than comparing vaccinated people to unvaccinated people, which invites the standard objection that healthier people simply choose to get vaccinated, Oxford researchers compared people vaccinated just before versus just after October 2017, the month Shingrix replaced the older Zostavax vaccine in the United States. Everyone in both groups chose to get vaccinated. Only the product differed. Using health records from 72,000 people aged 60 and older, the team found a 9 percent lower overall cardiovascular burden over seven years for Shingrix compared to Zostavax, including lower rates of coronary heart disease, heart failure and atrial fibrillation.

The mechanism both papers point to

The proposed explanation is the same one wellness content already sells against, chronic inflammation. Researchers point to AS01, an adjuvant present in Shingrix but not in the older Zostavax, and a concept called trained immunity, in which the vaccine appears to shift how immune cells behave more broadly rather than only training them to recognize the shingles virus. The fact that Zostavax, which lacks AS01, has not shown the same cardiovascular association in prior natural experiments is what makes the adjuvant explanation more than a guess.

Co author Fabiana Corsi Zuelli put it directly: the recombinant vaccine may induce trained immunity, meaning changes in cells of the immune system itself. Co author Maxime Taquet points specifically at AS01 as the likely driver, which is why the comparison against Zostavax matters so much to this whole argument. Neither researcher is claiming the mechanism is settled. They are pointing at where the next round of research needs to look.

Independent researchers reacted with real interest but real caution too. Kaleen Hayes, the dementia study's own lead author, is unaffiliated with the Oxford heart work and told reporters there has been very conflicting evidence on cardioprotection specifically, which is a fair summary of how young this particular finding is. The dementia signal looks steadier by comparison, now showing up across several independent datasets including an earlier Welsh natural experiment and a 2024 Nature Medicine report, which is part of why that half of the story reads as more settled than the heart half does.