4 Surprising Benefits of the Flu Shot

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Not getting sick from the flu is reason enough to roll up your sleeve for a flu vaccine every fall. And along with preventing millions of cases of influenza each year, flu shots also reduce hospitalizations for complications of this misery-making seasonal illness.

A 2021 study from researchers at the Centers for Disease Control and Prevention (CDC) found that adults who got vaccinated were 26 percent less likely to be admitted to the intensive care unit and 31 percent less likely to die from the flu compared to those who were unvaccinated. There seems to be protection from illness even when vaccines aren’t perfectly matched to the strain of flu virus circulating (since the shot is formulated months in advance).

But evidence suggests that there are other payoffs beyond defense from fever, fatigue, chills and aches.

“People don’t really appreciate the other potential benefits of flu shots,” says Michelle Barron, M.D., senior medical director of infection prevention and control for UCHealth in Aurora, Colorado. “It’s actually arming your immune system to fend off other problems.”

Here are four unexpected ways a flu vaccine can benefit the body and the brain.

1. A boost for the brain?

Previous research has suggested that flu vaccines may protect the brain from dementia, and a new study from the McGovern Medical School at UTHealth in Houston makes the case even stronger.

This study, published in the , compared more than 47,000 people age 65 and older who were vaccinated against flu to a similar group of nearly 80,000 people who were not vaccinated. The findings: Those who got a flu shot were 40 percent less likely to develop Alzheimer’s disease over a four-year period.

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“We weren’t actually expecting it to be that high,” says study coauthor Avram S. Bukhbinder, M.D., now a neurologist at Massachusetts General Hospital in Boston.

Bukhbinder has several theories for the vaccination’s potential effects on the brain. Perhaps by preventing the flu, the shot quells inflammation that can lead to harmful brain changes.

His most intriguing hypothesis is that vaccines alter the brain’s overall defenses. “There’s good evidence that when we get these vaccines, they help us make antibodies to the specific pathogen — the influenza virus,” he says. “But they may also modify the immune system in such a way that it’s better at either cleaning up amyloid and tau [the proteins responsible for the plaques and tangles that are the hallmarks of Alzheimer’s] or by preventing these proteins from building up in the first place.” 

2. The shot is linked to a stronger heart

A history of heart disease or a stroke can make flu more likely and more dangerous. In addition, flu can be a trigger for heart attacks and strokes in people at high risk for them. 

According to a 2018 Canadian study, people who got the flu were 6 times more likely to have a heart attack within a week of getting the diagnosis. And Columbia University researchers saw a significant jump in strokes in the month after fighting the flu, according to new research published in the American Heart Association’s journal . 

A flu shot can also spare you the potential heart harms. A new study led by the University of Toronto that incorporated six previous studies covering more than 9,000 patients showed that people who received a flu vaccine had a 34 percent lower risk of a major cardiovascular event in the 12 months following vaccination. Higher-risk vaccinated individuals with acute coronary syndrome — a group of conditions that abruptly stop blood flow to the heart — had a 45 percent risk reduction of major cardiovascular event, and a 56 percent reduced risk of dying from heart disease in the year after they got the shot, according to the findings, which appear in . How the flu shot protects the heart isn’t fully known, but it may have to do with the plaques that build up on artery walls of people with heart disease. The body’s immune response to the flu creates inflammation that is believed to disrupt these fat deposits, causing blood clots that may trigger heart attacks and strokes.

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“The vaccine may interact with the body’s immune system and inflammatory processes to help stabilize plaques that might be present in blood vessels, thus preventing these plaques from rupturing and causing further problems,” says lead study author Bahar Behrouzi Homa, an M.D./Ph.D. candidate at the university. 

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About the Author: Tung Chi