Scientific evidence suggests that shingles vaccination may come with an unexpected benefit: it can reduce the risk of developing cognitive decline associated with Alzheimer’s and other types of dementia and even slow the progress of these conditions.

Herpes zoster, commonly known as shingles, is a condition caused by the varicella‑zoster virus, which also causes chickenpox. This virus can remain dormant in the body for a long time. If VZV “wakes up” and reactivates, it can cause painful skin rashes, with residual secondary pain that can last for years.

To prevent this, shingles vaccination is recommended in people over 50 years, the population group that may have been exposed to the virus and might still harbor it in their bodies.

This virus, which causes shingles when reactivated, “hides” in the nerve tissue for decades after initial chickenpox infection. This “presence” may impact the peripheral nerves and cause inflammation. This neuroinflammation is a recognized risk factor for dementia.

A series of studies from the past three years hypothesized that VZV’s action on the tissues may increase dementia risk; therefore, vaccination could counteract this additional risk.

Some studies did not find a statistically significant association between herpes zoster and the risk of developing dementia, but others did. What a 2024 study did determine is that even though there was no clear added risk of dementia in people with shingles, herpes zoster vaccines may confer some cognitive protection. The meta‑analysis concluded that herpes zoster vaccination was associated with a modestly reduced risk of cognitive decline.

However, another article confirmed that receiving the recombinant herpes zoster vaccine (compared to one with a weakened live virus) was associated with a 17% increase in diagnosis‑free time during a six‑year follow‑up.

Vaccines are designed to protect against specific infections, but some research studies suggest that they may have unexpected non‑specific effects that improve the immune system’s ability to fight other diseases.

These combined effects help explain why vaccinated people may experience increased resistance to infections beyond those against which the vaccine was initially designed to protect. A more robust immune system can prevent cognitive decline by reducing inflammation (a trained immune system can neutralize a threat more quickly, reducing the amount of time the inflammatory process occurs). The hypothesis that this may prevent cognitive decline and slow the progress of dementia becomes even more plausible when it comes to diseases with neurotropism (the tendency to attack neural tissue, which is exactly what herpes zoster does).

The value of vaccines in general—all adulthood vaccines, not just herpes zoster—as indirect reducers of dementia risk is well known. The logic is simple: more vaccines mean fewer diseases, less chance of inflammation, and, therefore, a reduced risk of Alzheimer’s.

An article analyzing the protective factor of adult vaccines for dementia made a clear finding: of the 17 studies analyzed, with a total of 1,857,134 participants, the overall pooled results showed that vaccines were associated with a 35% lower dementia risk.

Dementia (and its most common form, Alzheimer’s), is the progressive loss of cognitive functions, such as thinking, memory, and reasoning, to the point that it interferes with a person's daily life and activities. Although it is known that a healthy lifestyle can reduce risk factors for dementia, the actual cause of this condition remains a mystery to scientists.

Dementia affects millions and is more common as people age (almost a third of all people 85 years or older may have some form of dementia), but it is not a normal part of aging. Many people live up to 90 years or older without any signs of dementia.

Despite the number of people living with dementia, scientists have yet to determine the origin and causes of this degenerative condition. For example, certain proteins, such as the Tau protein, are known to impact disease progression.

Encouraging adults—especially older adults—to get their vaccines appears to remain the key health strategy to prevent various conditions, including dementia.