Higher-dose flu vaccine linked to lower Alzheimer's risk in older adults
A US study of nearly 200,000 people aged 65 and over found that the high-dose flu vaccine was associated with a nearly 55% lower Alzheimer's risk. The standard dose was linked to a 40% reduction, but researchers stress this is an association, not proven cause and effect.
Older adults who received a high-dose flu vaccine were less likely to develop Alzheimer's disease than those given the standard-dose shot, according to researchers at UTHealth Houston, the University of Texas Health Science Center at Houston in the United States. The findings, published in the medical journal Neurology, come from an analysis of data on nearly 200,000 men and women aged 65 and older. Alzheimer's is the leading cause of dementia.
What the results showed
Standard-dose flu vaccination was associated with a 40% lower risk of Alzheimer's, while high-dose vaccination was linked to a reduction of nearly 55%. The association appeared stronger among women, who seemed to gain a larger risk reduction from the stronger vaccine.
The researchers stress that the results show an association rather than cause and effect. More studies are needed to determine whether high-dose vaccination directly lowers the likelihood of the disease and to explain what mechanism might be involved.
Why seniors get a stronger vaccine
With age, the immune system becomes less effective at recognizing and fighting infections, which makes influenza especially dangerous for older people. The US Centers for Disease Control and Prevention (CDC) recommends high-dose vaccines as a preferred option for adults 65 and older. They contain four times as much influenza antigen as standard shots; antigens are the components that prompt the immune system to recognize a virus. Before 2022, the CDC expressed no preference among injectable flu vaccines.
Demand for high-dose vaccines sometimes exceeds supply, so some seniors receive the standard dose. That variation allowed the team to compare the two groups.
How the study began
In 2022, a team led by neurologist Paul Schulz found that flu vaccination was associated with a lower Alzheimer's risk in people over 65. Public health officials who learned of that work asked whether dosage made a difference. Schulz, the senior author and director of the Neurocognitive Disorders Center at UTHealth Houston Neurosciences, said he had not known a higher dose existed.
In 2025, more than 7 million Americans aged 65 and older were living with Alzheimer's, about 1 in 9 people in that age group. The figure is projected to more than double by 2050.
