April 8, 2026, 6:52 pm | Read time: 4 minutes
The conflict between vaccine opponents and supporters escalated during the COVID-19 pandemic. A recent study supports the position of vaccine advocates, albeit with a rather unexpected positive vaccination effect. Apparently, there is a link between a high-dose flu vaccine and a reduced risk of Alzheimer’s.
The Standing Committee on Vaccination (STIKO) recommends an annual vaccination against seasonal influenza, especially for older people over 60 and risk groups (such as those with chronic illnesses, healthcare personnel, etc.).1
Colloquially, we refer to the flu shot, which protects against severe illness. However, U.S. researchers at Massachusetts General Hospital in Boston have identified another positive effect in a study. According to their research, there is a link between a high-dose flu vaccine and a lower risk for older adults of developing Alzheimer’s dementia.2
What Did the Researchers Examine?
The study included only older adults who had received a flu vaccination. The participant data comes from the years 2014 to 2019 from the U.S. health database “IQVIA PharMetrics Plus for Academics.” All study participants were at least 65 years old, had continuous health and medication insurance for at least two years, and showed no signs of cognitive impairment.
All had received a flu shot and were subsequently monitored for health over two to three years. Newly occurring Alzheimer’s dementia during this period was defined using diagnosis codes or billing for one of four medications used to treat Alzheimer’s symptoms.
The researchers defined all flu vaccines approved in the U.S. during the study period for people over 50 in the standard dose as standard vaccines. The only high-dose vaccine approved by the FDA (U.S. Food and Drug Administration) for people over 65 in December 2009 was a concentrated formulation called “Fluzone High-Dose Quadrivalent.”
The average age in both groups was 74 years, and 57 percent of participants were women. Overall, more than 120,000 study participants received the high-dose vaccine, and about 44,000 received the standard dose.
What Is the Link Between a High-Dose Flu Vaccine and Alzheimer’s Risk?
The data analysis showed that the high-dose flu vaccine was associated with a lower risk of Alzheimer’s dementia compared to standard-dose vaccinations in the first 25 months after vaccination.
“The results show that the higher dose compared to the standard dosage resulted in a risk reduction of about 20 percent,” explained Dr. Paul Schulz, co-author of the study, in a press release from the McGovern Medical School at UTHealth Houston.3 He added that it is particularly interesting that the risk reduction is greatest in the first months after the injection, especially when the vaccine simultaneously protects against the influenza virus. Interestingly, the researchers suspect that the effects in the first seven months may partly be due to undiagnosed conditions.
Additionally, women who received a high-dose flu vaccine had a significantly lower Alzheimer’s risk than men in the first 13 months. For men, the risk of Alzheimer’s dementia was lower in months 17 to 24 after the high-dose vaccination.
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Researchers Had Already Found Evidence for the Link in Previous Studies
The current study is the latest in a series of investigations by the research team. For years, they have been analyzing the link between vaccinations and the risk, particularly for Alzheimer’s dementia.
“Our first publication from 2022 found that a flu vaccination reduces the Alzheimer’s risk by up to 40 percent—with six annual vaccinations—over a period of up to eight years,” Dr. Schulz told the news portal “MedPage Today.” This led him and his team to investigate whether this is specific to the flu vaccine.
In 2023, another study followed, showing that each of the vaccines examined (tetanus and diphtheria, herpes zoster (shingles), and pneumococcal) was associated with a later reduced Alzheimer’s risk.
“This suggested that reducing Alzheimer’s risk is a general property of vaccinations and not specific to the flu vaccine,” commented Dr. Schulz. This led to the question of whether there was a real connection or whether people who get vaccinated might generally lead healthier lives. And that, in turn, led to the current study.
Limitations of the Study
The researchers themselves point out that the mortality data of the study participants were missing in the current study. This could indicate that the Alzheimer’s risk was underestimated. Additionally, the researchers acknowledged that Alzheimer’s dementia has a long preclinical phase. The follow-up period of up to three years might be too short. This could be another limitation, although this study is comparable to other studies dealing with vaccinations and dementia risk.
The U.S. researchers call for further studies to clarify whether the effect is due to influenza protection or other factors such as lifestyle.