A high-powered flu shot might help reduce seniors’ risk of Alzheimer’s disease, a new study says.

Seniors who got a high-dose flu vaccine had a nearly 55% reduced risk of Alzheimer’s, researchers reported earlier this month in the journal Neurology.

This high-dose jab – four times stronger than the standard dose – is recommended by the U.S. Centers for Disease Control and Prevention (CDC) for folks 65 and older, researchers said.

Previous research has shown that the standard dose also reduces Alzheimer’s risk, but only by about 40%, researchers said.

Many people – including health care professionals – aren’t aware of this higher dose that’s available for seniors, said senior researcher Dr. Paul Schulz, a professor of neurology at the University of Texas Health Science Center at Houston.

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

Alzheimer’s is the most common form of dementia, affecting more than 7 million seniors as of 2025, researchers said in a news release. That number is expected to more than double by 2050.

For the new study, researchers compared nearly 121,000 seniors who received the high-dose flu shot with more than 44,000 who got the standard dose.

The high-dose shot is recommended because seniors’ immune systems start to falter as they age, becoming less effective at fighting infection, researchers said.

“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,” Schulz said. “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."

Results showed that those who got the higher dose had a significantly lower risk of Alzheimer’s than those who got the standard dose for at least 25 months.

Researchers also found the protective effect of the high dose was stronger among women.

The study couldn’t say why the flu shot might protect against Alzheimer’s, and could not draw a direct cause-and-effect link between the jab and lower risk.

Further research is needed to understand not only why the shot might help protect against Alzheimer’s, but also why a higher dose would work better, researchers said.