Flu Shots and Alzheimer’s: Is There a Connection?

The connection between Alzheimer’s disease and flu shots has been a long a widely disputed one. In the 1990s, a doctor in the USA has been wrongfully spreading misinformation about vaccinations, claiming that they are capable of causing Alzheimer’s disease. According to Verywellhealth, “This idea may come from Dr. Hugh Fudenberg, whose medical license was revoked in 1995. Some internet sites credit him as the source who states that the flu shot increases the risk of Alzheimer's”.
The former doctor’s false claims have spurred a negative attitude towards vaccination in the general population. To double-check that flu shots are safe to the public, a multitude of new studies have been conducted, and all of them found that flu shots do NOT cause Alzheimer’s disease, but they did find another very curious correlation. Starting from 2001, studies started appearing that claimed the opposite was actually true and vaccinations can lower one’s risk of Alzheimer’s. More on that below.

How vaccines can help prevent Alzheimer’s Disease

Vaccines and Alzheimer's Disease old man sitting in couch
In a surprising turn of events, the outrage towards vaccinations has led to an exciting discovery that can potentially help millions of people at risk of Alzheimer’s and dementia protect themselves from cognitive decline. As of 2020, there are several studies confirming that vaccinations can lower the risk of Alzheimer’s disease.
The first study of the kind was conducted in 2001 in Canada and researched the population of 4392 adults 65 and older who were either vaccinated or not, and they conclude that vaccination may actually lower one’s risk of Alzheimer’s. Quoting the study, “Past exposure to vaccines against diphtheria or tetanus, poliomyelitis and influenza may protect against subsequent development of Alzheimer's disease”.
More recent research coming from 2 different studies presented at the 2020 Alzheimer’s Association Virtual International Conference further specifies the positive effect of vaccines on brain health. In the first study conducted at the University of Texas, researchers looked at the health records of more than 9,000 seniors in the age range of 60 and older.
Vaccines and Alzheimer's Disease flu shot

The researchers found that even those who only received a flu vaccine once in their lifetime had a 17% lower risk of developing Alzheimer’s. Those who got two flu shots or got vaccinated regularly had even better protection from the disease - a 30% percent lower risk.
The second study found a very similar result. It was conducted in a different part of the US as a joint project between Duke University and the University of North Carolina. This research looked at 5,000 people aged 65+, concluding that those who got a pneumonia vaccination at least once before age 75 has a 25-30% lower likelihood to develop Alzheimer’s. These findings are pretty impressive, and medical research is now considering vaccination as a possible preventative treatment of Alzheimer’s!
It also needs to be said that flu and pneumonia vaccines are beneficial not only as a preventative tool but also as a lifesaving treatment for dementia and Alzheimer’s patients. This is because hospitalized dementia patients are over six times more likely to die as a result of an infection, and catching the flu or any other respiratory infection can actually further worsen their symptoms and even lead to delirium. Therefore, medical professionals stress the importance and great value of yearly vaccinations for all seniors, especially dementia and Alzheimer’s patients.

Why do vaccines help prevent Alzheimer’s?

Vaccines and Alzheimer's Disease injection
Given the relative novelty of these findings, researchers don’t really know yet how exactly flu shots and other vaccines are capable of preventing Alzheimer’s disease. They do point out, however, that many previous studies have suggested that inflammation and recurrent infections may increase one’s risk of dementia and cognitive decline. Influenza, or the common flu, has been shown to cause this kind of long-term brain inflammation, as shown in a 2018 study. This way, preventing influenza may also help put a stop to cognitive decline, too. 
Certain research has even tried linking specific strains of bacteria, fungi, or viruses to Alzheimer's disease, but the current consensus is that the brain conditions are worsened by chronic inflammation and infections instead of being directly caused by any specific microbe.
In addition, recurring respiratory infections may be lowering your immune system, which may also raise your risk of dementia. As Dr. Kaiser, the director of Geriatric Cognitive Health for Pacific Neuroscience Institute at Providence Saint John’s Health Center, stated to Healthline, “Getting sick with the flu or pneumonia, particularly with bad cases, can be taxing on the brain and increase your long-term risk of dementia. So protecting yourself from flu and pneumonia, through vaccination, may very well be protecting your brain too", and we completely stand by that final piece of advice.
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