While lifesaving vaccines face a relentless onslaught from the Trump administration—with fervent anti-vaccine advocate Robert F. Kennedy Jr. leading the charge—scientific literature is building a wondrous story: A vaccine appears to prevent dementia, including Alzheimer’s, and may even slow biological aging.

For years, study after study has noted that older adults vaccinated against shingles seemed to have a lower risk of dementia. A study last month suggested the same vaccine appears to slow biological aging, including lowering markers of inflammation.

“Our study adds to a growing body of work suggesting that vaccines may play a role in healthy aging strategies beyond solely preventing acute illness,” study author Eileen Crimmins, of the University of Southern California, said.

Another study this month suggested the positive findings against dementia from the past may even be underestimates of the vaccination’s potential, with a newer vaccine against shingles providing even more protection.

Shingles

If the dementia protection is real, it’s a fluke. The vaccine was designed for the entirely unrelated task of keeping the varicella-zoster virus—the cause of chickenpox (varicella)—from reactivating and causing an agonizing rash.

Anyone who suffered the itchy childhood affliction carries the virus with them for the rest of their lives, largely dormant in their nerve cells. But, if it awakens, it causes a painful, itchy rash—aka shingles (herpes zoster). The rash develops fluid-filled blisters and crusts over, lasting for days to several weeks. For some, it can be intensely painful, and the pain can linger for months or even years after the rash fades. If it occurs near the eye, it can cause permanent vision damage; near the ear, it can cause permanent hearing and balance problems.

Shingles is thought to be triggered by a fault in the immune response that keeps the latent virus in check, often from age-related decline. That’s where a vaccine comes in. The first was Zostavax, released by Merck in 2006, which delivers a hefty dose of a live, but weakened, version of the varicella-zoster virus. This spurs the immune system to shore up defenses to prevent the virus from reigniting. Studies found the vaccine cut the risk of shingles by 51 percent.