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Sunday 21st July 2019

Flu jab may protect the heart

29th October 2012

Researchers in Canada say that flu vaccines may not just guard against influenza; they may also protect against cardiovascular disease.


In two small, preliminary studies of heart patients, researchers found that those who had received influenza jabs had a lower risk of cardiovascular events like strokes or heart attacks.

The researchers presented their findings at the 2012 Canadian Cardiovascular Congress, prompting calls for larger studies to see if the findings were repeatable.

According to researcher Jacob Udell of the Women's College Hospital in Toronto, the study's findings were "provocative," because they showed that 7.8% of patients who received no flu shots had a major cardiovascular event in the course of one year, while only 4.3% of those who received flu shots experienced them.

That represents a reduction in risk of a major cardiovascular event of nearly 50%.

The study looked at data from four existing clinical trials that examined the effects of flu vaccines in 3,200 patients, half of whom had heart problems, and half of whom had no history of cardiovascular disease.

Major cardiovascular events were defined as heart-related deaths and non-fatal heart attacks, strokes, emergency heart procedures, or hospital admissions for heart failure or sudden chest pain.  

The team concluded that, for every 34 people who receive an influenza vaccine, one major cardiovascular event is prevented.

A second study at the same hospital looked at 230 patients with implanted cardiac defibrillators (ICDs), which shake the heart out of dangerous, irregular rhythms.

The devices seem to work harder during the winter months, and the study set out to see whether this had something to do with influenza viruses.

The study showed that the 80% of patients who received their flu jab had fewer ICD shocks overall than the 20% who did not get the influenza vaccine.

According to research team member Sheldon Singh of the University of Toronto, the findings were thought-provoking, especially if they were repeated in larger studies.

According to Udell, flu vaccines could help the heart by protecting vulnerable patients from the respiratory problems, and consequent lack of oxygen, that comes with influenza.

But they might also protect unstable buildups in artery walls from breaking open and cutting off blood flow to the heart or brain.

Artery-clogging plaques are prone to rupture, and these ruptures may be triggered by inflammation caused by viral infections.

But Jennie Johnstone, assistant professor in the division of infectious diseases at Toronto's McMaster University, said that follow-up studies would be needed to confirm the findings.

She said the current body of evidence made it difficult to tell whether influenza vaccination really reduces cardiovascular events.

According to recommendations from the US Centers for Disease Control and Prevention, all adults, including those with underlying conditions like heart disease or diabetes, should get the influenza vaccine every year, although most people do not follow this advice.

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