A 63-year-old viral immunologist from Colorado spent four years experiencing progressive cognitive decline — impaired memory, lost concentration, difficulty finishing sentences. Brain biopsies found nothing. The answer, eventually, was shingles.
After recalling a brief shingles episode before his symptoms began, the lecturer tested positive for a reactivation of the varicella-zoster virus. A course of acyclovir, a standard antiviral, reversed his decline entirely. The case was published in 2016 and has driven a wave of neurovirological research into what the virus actually does to the aging brain.
A Virus That Never Leaves
Before routine chickenpox vaccination began in the US in 1995, more than 90 percent of children acquired varicella-zoster. After infection, the virus does not clear — it settles into the peripheral nervous system and goes dormant, sometimes for decades.
Reactivation can be triggered by stress, concussion, co-infection with Covid-19, immunosuppressive medications, or simply the natural aging of the immune system. In many cases, no visible symptoms appear. According to the report, multiple “subclinical” reactivations — the virus waking up without producing a rash — may occur repeatedly in mid- to later life without the person ever knowing.
“We rely on specialized immune cells to continuously patrol the nervous system and keep the dormant virus suppressed,” says Tian-Shin Yeh, associate professor of medicine at Taipei Medical University. “As we get older, these cells can become less effective, or exhausted.”
Andrew Bubak, assistant professor of neurology at the University of Colorado Anschutz, says the true burden of varicella-zoster “is totally underestimated. But it’s a very treatable virus.”
Dementia Links and the Vaccine Question
Shingles has long been associated with postherpetic neuralgia — nerve pain once cited as the leading cause of pain-related suicide in the elderly. Researchers are now identifying a separate burden on the brain.
Two independent studies have found associations between shingles and both self-reported cognitive decline and dementia. A Stanford University study published in April 2025 suggested the shingles vaccine could prevent one in five new dementia cases. More recent research has also linked vaccination to slower biological aging across multiple measures.
One proposed explanation is that the vaccine broadly stimulates the immune system in a beneficial way. Researchers increasingly believe, however, that avoiding varicella-zoster reactivation in the first place may be the more direct mechanism.
The childhood chickenpox vaccine — standard in the US since 1995 and introduced in the UK in January 2026 — reduces the initial infection rate. Adult shingles vaccines and booster shots in later life offer a second line of defense. Neurovirologists say both matter, given that the virus’s effects on the brain may accumulate silently, long before any clinical symptoms emerge.
Photo by Rick Rothenberg on Unsplash
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