Can You Get Shots to Protect You from Alzheimer Disease?

Have you ever heard the old story about a person searching for lost keys under a streetlamp? When asked why look there, the answer was simple: “That’s where the light is.” Researchers studying Alzheimer disease (AD) may have been doing something similar for decades. They have been searching for drugs to remove amyloid from the brains of patients with dementia. But perhaps they should have been experimenting with shots to protect us from Alzheimer disease or other types of dementia.

What Is Amyloid Plaque?

This sticky protein plaque made of beta-amyloid is a prominent feature of AD. Scientists believed it was responsible for neuronal destruction, memory loss and disability. Pharmaceutical companies spent billions of dollars chasing drugs to remove amyloid plaque from the brain. The results have been deeply disappointing. Many studies flamed out completely. Other drugs slightly slowed cognitive decline, but did not restore memory or function.

What About Shots to Protect People from Dementia?

When researchers started studying the function of beta-amyloid in the brain, they made some interesting discoveries. Beta-amyloid has potent antimicrobial properties. Some researchers believe that the buildup of amyloid plaque occurs in response to an infectious assault on the brain. In other words, amyloid is a natural defense mechanism to an attack from a pathogen.

This hypothesis has gotten unexpected support over the past few years from vaccine research. Natural experiments demonstrate that shots to protect us from shingles and others targeting the flu can also reduce our risk of developing dementia. We’ll take them one at a time, starting with the shingles vaccine.

What Do We Know About the Shingles Shot Against Dementia?

Three independent population-wide studies now suggest that this humble shot may modestly reduce dementia risk, forcing medicine to ask whether it’s time to look beyond the lamp post. These natural experiments involve an old shingles vaccine, Zostavax. Doctors recommend it to reduce the chance of a painful attack of shingles, which could occur to anyone who had chickenpox as a child. This latest research reinforces the theory that herpes virus can contribute to Alzheimer disease. (Herpes and chickenpox are related viruses.)

Natural Experiments:

There have been two prior studies of this vaccine. The first was set in Wales and the other examined data from Australia. In that research, scientists took advantage of “natural experiments.” In these countries, healthcare policymakers established arbitrary eligibility dates for people to receive the vaccine. People only slightly older did not differ from those who were eligible in other important respects, but they could not be vaccinated. Because the vaccines were provided, most people who were eligible chose vaccination.

As a result, the protective effects of the vaccine were clear. Welsh seniors who had been vaccinated were 20 percent less likely to be diagnosed with dementia over the next several years (Nature, April 2, 2025). That is a relative risk. The absolute difference was 3.5 percent.

Australians Also Controlled the Shingles Vaccine Roll-out:

In Australia, people eligible for the shingles vaccine were 1.8 percent less likely to develop dementia (JAMA, April 23, 2025). That is the difference in absolute risk. The investigators determined that eligibility for the shingles vaccine did not change the risk of 15 other common conditions, only dementia.

What Happened in Canada:

The most recent study comes from Canada (Lancet Neurology, Feb. 2026). In Ontario, people born on or after Jan. 1, 1946, were eligible for the shingles vaccine. Electronic health records from 1990 to 2022 demonstrated an absolute difference in dementia diagnoses of 2 percentage points between those eligible for the shingles shot and those who missed it by a few weeks or months. Elsewhere in Canada, where there was no shingles vaccination program, there is no clear difference in risk of dementia by birth date.

The investigators write:

““In conclusion, this study provides strong evidence of a protective effect of herpes zoster vaccination on incident dementia.”

These three natural experiments reinforce the idea that amyloid plaque buildup may be a reaction to infection. Hopefully, future research will reveal even more effective ways to delay, prevent or treat dementia. We now know it’s not crazy to look for shots to protect elders from Alzheimer disease. We turn now to earlier evidence on the protection offered by influenza vaccinations.

Vaccine Skeptics Doubt Flu Shots Protect Them!

The anti-vax movement has been gathering steam for years. Many parents are choosing not to vaccinate their children against measles, mumps and rubella (MMR). Perhaps that is why we have seen several measles outbreaks over the past few years. South Carolina’s current outbreak is the largest in the US since 2000. It has affected more than 876 children so far.

I try to be objective about vaccinations, recognizing both the benefits and the risks. To be perfectly honest, though, I have a hard time being totally impartial. That’s because when I was under the age of three I caught polio. I spent weeks in the Children’s Hospital of Philadelphia in a polio ward. I was immobilized in traction and was surrounded by children who were dying of this highly infectious disease. You can read more about the polio story at this link.

I also caught whooping cough (pertussis) as a child. My parents were afraid it might kill me. The coughing fits were horrific and I often struggled to breathe. People who  oppose vaccines have no idea what it’s like to deal with polio or whooping cough. If their kids develop either infectious disease, though, it will leave an indelible impression.

What About Influenza Vaccines?

Although most doctors are confident flu shots protect you from influenza, the level of protection varies dramatically from year to year. Unfortunately, older people who are at highest risk from flu infections are less likely to have a strong immune response to the vaccination.

We have written extensively about disappointing influenza vaccine results. That’s because flu shots are highly variable one year to the next. Some years the vaccine is only 10 to 20% effective while other years it works 40-60% of the time. You can see my most recent breakdown of vaccine effectiveness at this link.

Could Flu Shots Protect People from Alzheimer Disease?

Even if you are not impressed by the vaccine’s effectiveness against the flu, there may be another reason to roll up your sleeve. Many scientists have found that people who get their shots every year are less likely to develop dementia.

Previous studies have linked immunization to a reduced risk for dementia (Journal of Alzheimer’s Disease, Aug. 2, 2022). To find out if flu shots protect from Alzheimer disease specifically, investigators analyzed a large database of de-identified insurance claims. These included more than two million people over 65.

The researchers divided the data into matched pairs of people who did or did not get their flu vaccines. After nearly four years of follow-up, they found fewer vaccinated individuals had developed Alzheimer disease. To be precise, 5.1% of the vaccinated and 8.5% among those who had not gotten their shots now had Alzheimer disease. Consequently, the absolute risk reduction is over 3%, with a relative risk reduction around 40%.

Previous Studies on Whether Flu Shots Protect Folks from Dementia:

A surprising number of studies indicate that flu shots protect us from cognitive dysfunction. Of course, most of these are observational studies. Scientists don’t fully trust conclusions based on such data. For example, people who are most likely to be conscientious about influenza immunization may also be health-conscious in other ways. Nonetheless, other scientists have reported on this phenomenon.

Flu Shots for Veterans:

A team from St. Louis University evaluated medical records from the Veterans Health Administration (Vaccine, Sep. 15, 2021). This patient population was older, mostly male and predominantly white. The 66,822 patients who sought annual flu shots were significantly less likely to become demented. That was in comparison to 56,925 patients who chose to skip the shots. Protection kicked in at six or more years of flu vaccination.

The authors conclude:

“Repeated receipt of influenza vaccinations, compared to remaining unvaccinated, is associated with lower risk for dementia. This is consistent with the hypotheses that vaccinations may reduce risk of dementia by training the immune system and not by preventing specific infectious disease. If vaccines are identified as causative factors in reducing incident dementia, they offer an inexpensive, low-risk intervention with effects greater than any existing preventive measure.”

Two Types of Vaccinations:

After analyzing the VHA data, the researchers wanted to replicate their study in a different group of patients. For this, they chose private sector medical claims data (Journal of the American Geriatrics Society, April 2022). In addition, they considered whether people receiving different types of immunization got more protection. The medical claims data covered 129,200 people, while the VHA data used for this study included 80,070.

Instead of asking whether flu shots protect seniors from dementia, they wondered whether people who got different vaccines did better than those who received only one type of shot. To determine this, they compared people who got both a shingles shot and a tetanus booster (Tdap) to people vaccinated only against shingles or only against tetanus. They also examined data on people with no vaccinations. In both data sets, two different immunizations protected people from dementia compared to no vaccinations.

In their conclusion, the authors wrote:

“Vaccinations may have non-specific associations with incident dementia. Low cost and accessible, common adult vaccinations may be an overlooked intervention for reducing dementia risk.”

Why Would Flu Shots Protect Against Dementia?

There is a growing suspicion that infections may “reactivate” latent viruses that are lurking in the body. You can read about this phenomenon in this article about the anti-herpes drug Valtrex against symptoms of long COVID.

Of course this is hypothetical and needs to be fully tested. But if the concept of reactivation holds true, then preventing herpes outbreaks might be beneficial. This could also hold true for influenza outbreaks.

Learn More:

You may wish to listen to these podcasts on Alzheimer disease and dementia. One is Show 1451: Rethinking Dementia: Is What We Believed About Dementia Wrong?  The other is Show 1394: Viruses, Vaccines and Alzheimer Disease. If you have found this post valuable, why not share it with your family and friends? It helps us to get the word out.