Getting a Flu Shot Might Lower Stroke Risk

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Key Takeaways

  • A new study links the flu shot to a lower risk of having a stroke.
  • Researchers think this may have to do with avoiding viral illness or mediating inflammation.

Getting your annual flu shot may do more than lower your risk of influenza. A new study has tied the flu shot to a lower stroke risk.

The study, which was published in the journal Neurology, showed that people who received their annual flu shot had a 12% lower risk of developing a stroke compared to those who did not receive a flu shot, even when other stroke risk factors were considered.

Researchers analyzed data from about 14,000 adults in Spain who were at least 40 years old and had experienced a stroke. Those study participants were compared to about 70,000 people who did not have a history of stroke. The researchers then analyzed factors that could have impacted stroke risk over a 14-year period.

Study co-author Francisco J. de Abajo, MD, MPH, PhD, a professor of pharmacology at the University of Alcalá, told Verywell that he and his research team decided to study this link after discovering that having the flu is tied to an increased risk of acute myocardial infarction—a heart attack—and that being vaccinated against the flu lowered this risk.

The next logical step was to explore if the influenza vaccine could also protect from having an ischemic stroke,” de Abajo said.

But why might having the flu vaccine lower your risk of stroke? Here’s what you need to know.

What Happens During a Stroke?

A stroke, which is also known as transient ischemic attack, is what happens when blood flow to the brain is blocked. This prevents the brain from getting necessary oxygen and nutrients from the blood—and brain cells start to die within minutes when this blockage occurs. Stroke may also be caused by bleeding in the brain.

A stroke is a medical emergency, and it can lead to brain damage, disability, and even death. Symptoms of a stroke can vary, but generally include:

  • Weakness, paralysis, or numbness on one side of the face or body
  • Sudden and severe headache
  • Difficulty seeing
  • Trouble speaking or understanding speech 

Why Might Getting a Flu Shot Lower Your Stroke Risk?

The study didn’t explore the reason for the stroke protection conferred by a flu shot, but de Abajo said there are a few theories. One is that the flu shot helps prevent the flu—and avoiding viral illness lowers the risk that you’ll develop a heart attack or stroke.

Another is that the flu shot can help mediate inflammation in your body. Inflammation, he explained, can raise your risk of having a stroke.

Contracting the flu can also cause after-effects that could raise the risk of having a stroke, Pedro Piedra, MD, a professor of molecular virology and microbiology at Baylor College of Medicine, told Verywell.

"We always think about influenza infection as just giving you the flu, but a lot of people die from influenza on a regular basis—not just the acute infection, but also from problems they develop down the road," he said. "This can have longer-term consequences that can increase your risk of dying once you’ve been infected."

It's also entirely possible that people who get their annual flu shot tend to be healthier, de Abajo said.

"This is not easy to prove, as such healthier habits are not properly recorded in the clinical records of patients,” he said. Still, de Abajo pointed out that his research team didn’t find a link between lowered stroke risk and getting the pneumococcal vaccine. He also noted that “the most benefited people from flu vaccination are precisely those at a higher risk of having a stroke—not the healthy ones.”

It's unclear why the pneumococcal vaccine isn’t linked to a lower risk of stroke and the flu shot is, but de Abajo said it may simply be because they’re designed to target different things. The pneumococcal vaccine is designed to protect against a bacterial form of pneumonia, while the flu is a viral infection.

"It is not unexpected that they have different effects, but the people who use them are more or less similar,” he added.

Ultimately, Piedra said it’s important for everyone to get their annual flu shot. “The flu can have an acute and long-term impact on us,” he said. “Preventing it is very important.”

What This Means For You

Getting an annual flu shot is an important way to protect against serious complications of influenza—and it may also lower your risk of having a stroke. Getting your shot as recommended is a crucial way to stay healthy during flu season, and possibly beyond that.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Rodríguez-Martín S, Barreira-Hernández D, Gil M, García-Lledó A, Izquierdo-Esteban L, De Abajo FJ. Influenza vaccination and risk of ischemic stroke: A population-based case-control studyNeurology. Published online September 7, 2022. doi:10.1212/WNL.0000000000201123

  2. García-Lledó A, Rodríguez-Martín S, Tobías A, et al. Relationship between influenza, temperature, and type 1 myocardial infarction: An ecological time-series studyJAHA. 2021;10(8):e019608. doi:10.1161/JAHA.120.019608

  3. National Heart, Lung, and Blood Institute. What Is a stroke?

By Korin Miller
Korin Miller is a health and lifestyle journalist who has been published in The Washington Post, Prevention, SELF, Women's Health, The Bump, and Yahoo, among other outlets.