Flu Shot Might Prevent Stroke

Flu vaccine tied to significantly decreased risk of stroke and mini stroke

(RxWiki News) Doctors recommend annual flu shots to help patients stay healthy during flu season. New research suggests that the flu vaccine also might help prevent stroke.

A team of researchers examined vaccination records for patients who had and had not been diagnosed with stroke.

These researchers found that people who had gotten a flu shot were significantly less likely to have a stroke that year.

According to the authors of this study, respiratory infections put stress on the circulatory system, which may be why flu shots were tied to a lower stroke risk.

"Get an annual flu vaccine."

A. Niroshan Siriwardena, of the Community and Health Research Unit in the University of Lincoln in the UK, led this study.

According to Siriwardena and colleagues, respiratory infections like the flu or pneumonia can trigger a stroke by putting stress on the circulatory system.

Strokes occur when not enough blood is reaching the brain. Similarly, transient ischemic attacks (TIAs), often referred to as mini-strokes, occur due to a loss of blood flow to the brain.

Mini-strokes resolve faster than strokes, but they also increase a person's risk for having a stroke.

Because respiratory symptoms have been tied to stroke risk, Siriwardena and team conducted this study on whether flu or pneumonia vaccines can reduce stroke and mini-stroke risk.

These researchers used data on 26,784 patients who had strokes and 20,227 patients who had mini-strokes.

Each case was matched with a "control" patient's data. Case and control patients were matched for age and sex and visited the same medical practice.

The researchers analyzed the patient data to see if vaccinated patients had a reduced risk of stroke.

They found that the flu vaccine was tied to a 24 percent reduction in stroke risk.

Patients who had received a vaccine early in the flu season, from September to mid-November, had a lower stroke rate than those who had been vaccinated later.

The risk reduction lasted for 12 months after the vaccination date.

Flu vaccination did not reduce patients' risk of a mini-stroke.

Pneumonia vaccines did not reduce the risk of stroke or mini-stroke.

"The results of this study appear to confirm the results of previous studies that flu vaccination can indeed be beneficial in helping to reduce the risk of cardiac and stroke-related illness associated with influenza," said E. Lee Carter, RPh, Clinical Pharmacy Specialist at the Department of Veterans Affairs in Prestonsburg, Kentucky.

"Retrospective investigation reveals that 37 percent of adults hospitalized with the flu during the 2010-2011 flu season had underlying heart disease, which can be a primary contributor to the risk of developing stroke or TIAs (transient ischemic attacks or 'mini-strokes'). The authors surmise that influenza places increased workload on the cardiovascular system, thereby increasing the risk of stroke in patients predisposed to such conditions," Carter said.

The authors of this study acknowledged that there were some limitations to their research. For example, healthier adults may be more likely to receive a vaccine.

"The authors do point out the limitations of their work, including that younger, healthy adults tend to be vaccinated at a greater rate than those patients at greatest risk for cardiac or stroke problems. Nonetheless, this research adds to the larger chorus of experts who continue to maintain the health benefits of timely flu vaccination for all eligible patients," Carter told dailyRx News.

"Patients should check with their healthcare provider or pharmacist for further information on how the flu vaccination can help keep them and their family healthy," he said.

The researchers concluded that this study reinforces recommendations for annual flu vaccination. They suggested that flu vaccines would improve population health and could potentially prevent strokes.

This study was published in Vaccine on January 28.

The researchers declared that they had no conflicts of interest and did not receive financial support for the study.

Review Date: 
February 21, 2014