Getting a Flu Shot May Reduce Your Risk of Stroke

Annual flu shots are linked to a lower risk of stroke.

According to research recently published in the journal Neurology getting an annual flu vaccination may reduce the risk of stroke.

“Studies have shown that getting the flu increases your risk of having a stroke, but research is still being collected on whether getting the flu vaccine can help protect against a stroke,” said study author Francisco J. de Abajo, MD, MPH, Ph.D., of the University of Alcalá in Madrid, Spain. “This observational study suggests that those who have a flu shot have a lower risk of stroke. To determine whether this is due to a protective effect of the vaccine itself or to other factors, more research is needed.”

The most common kind of stroke, ischemic stroke, which is brought on by a restriction in blood flow to the brain, was the subject of the research.

In order to gather data for the study, researchers examined a Spanish healthcare database for individuals who were at least 40 years old and had their first stroke during the previous 14 years. Each stroke patient was compared to five other individuals of the same age and gender. The database included 71,610 individuals who did not suffer a stroke and 14,322 people who did.

The researchers then looked at whether patients had gotten the influenza vaccination at least 14 days prior to the stroke, or before that same date in the case of those who did not have a stroke.

A total of 41.4% of those who had a stroke had received the flu shot, compared to 40.5% of those who did not have a stroke. But the people who got the shot were more likely to be older and to have other conditions such as high blood pressure and high cholesterol that would make them more likely to have a stroke. Once researchers adjusted for those factors, they found that those who received a flu shot were 12% less likely to have a stroke than those who did not.

The researchers also looked at whether the pneumonia vaccine had any effect on the risk of stroke and found no protective effect.

“These results are yet another reason for people to get their yearly flu shot, especially if they are at an increased risk of stroke,” de Abajo said. “To be able to reduce your risk of stroke by taking such a simple action is very compelling.”

Reference: “Influenza Vaccination and Risk of Ischemic Stroke: A Population-Based Case-Control Study” by Sara Rodríguez-Martín, Diana Barreira-Hernández, Miguel Gil, Alberto García-Lledó, Laura Izquierdo-Esteban and Francisco Jose De Abajo, 7 September 2022, Neurology.
DOI: 10.1212/WNL.0000000000201123

Since the study was observational, it does not prove that getting the flu shot reduces the risk of stroke. It only shows an association. There could be other factors that were not measured that could affect the risk of stroke.

The study was funded by the Biomedical Research Foundation of the Prince of Asturias University Hospital in Madrid and the Institute of Health Carlos III in Madrid.