A closer look at vaccine strength revealed a surprising link to brain health.

A routine visit to a public health office led to an unexpected scientific insight, one that may reshape how researchers think about preventing Alzheimer’s disease.

A new study from UTHealth Houston reports that older adults who receive a higher dose of the influenza vaccine may have a significantly lower risk of developing Alzheimer’s disease compared to those who receive the standard dose.

The results were published in Neurology.

Alzheimer’s disease is the leading cause of dementia, affecting more than 7 million Americans age 65 and older as of 2025. That represents about 1 in 9 people in this age group, and the number is projected to more than double by 2050.

Earlier research from 2022, led by Paul Schulz, MD, a professor of neurology at McGovern Medical School at UTHealth Houston and director of the Neurocognitive Disorders Center, found that people age 65 and older had a lower risk of Alzheimer’s disease if they received a flu vaccine.

Now, three years later, Schulz and his team report that the reduction in risk is even greater among those who receive a higher dose of the vaccine.

A Question That Sparked New Research

“The public health department had seen our vaccine research and asked if I could come down to talk to them about it,” said Schulz, who is the senior author of the study and the Rick McCord Professor in Neurology and Umphrey Family Professor in Neurodegenerative Diseases at McGovern Medical School. “We went through the findings, and they asked if there was a difference with different dosages; I was confused.”

As people reach age 65, the immune system becomes less effective at fighting infections. For this reason, the CDC recommends a high-dose flu vaccine for adults in this age group, which is four times stronger than the standard version given to the general population.

“I was stunned that, as a physician, I didn’t know a higher dose was offered,” Schulz said.

Vaccine Use and Gaps in Knowledge

Flu vaccination is recommended for everyone, but influenza can cause more serious complications in people with Alzheimer’s disease.

Before 2022, the CDC did not favor one intramuscular flu vaccine over another for adults age 65 and older. The main recommendation was simply to get vaccinated each year, regardless of the formulation. Previous UTHealth Houston research showed that inactivated flu vaccines were linked to a 40% lower risk of Alzheimer’s disease, but no studies had examined whether higher doses could provide additional protection.

Schulz also noted that the aging population has strained the supply of high-dose vaccines in some areas. As a result, some individuals still receive the standard dose.

Comparing High- and Standard-Dose Vaccines

“So we started looking, and sure enough, we were able to put together thousands and thousands of people over the age of 65 who got the high- or low-dose vaccine. They’re more at risk for Alzheimer’s than anybody else, of course, because it’s age-related and we could look at high-dose versus low-dose and see if there was a difference,” Schulz said.

The team analyzed data from nearly 200,000 adults age 65 and older, including both men and women. The results showed that those who received the high-dose influenza vaccine had a lower risk of Alzheimer’s disease than those who received the standard dose. The protective effect was more pronounced in women.

Compared to the standard-dose flu vaccine, which was associated with a 40% reduction in Alzheimer’s risk, the high-dose vaccine was linked to nearly a 55% reduction in risk among adults age 65 and older.

Reference: “Risk of Alzheimer Dementia After High-Dose vs Standard-Dose Influenza Vaccination” by Avram Samuel Bukhbinder, Yaobin Ling, Lauren Jhin, Elizabeth He, Kristofer Harris, Mya Rodriguez, Jenna Thomas, Gabriela Cruz, Kamal Phelps, Yejin Kim, Luyao Chen, Xiaoqian Jiang and Paul E. Schulz, 1 April 2026, Neurology.
DOI: 10.1212/WNL.0000000000214782

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