The risk of a heart attack is reduced by almost one-third in older people who have the flu jab compared with those who don't, a study shows.

The flu jab doesn't just keep the virus away, it can reduce the risk of a heart attack for people over 50.

The risk is reduced by 29 per cent when compared to those who haven't been vaccinated, according to a UNSW study published in the journal Heart.

That's in the same ballpark as other heart attack preventative measures such as stopping smoking, anti-hypertensive medications and statins, says senior author Professor Raina MacIntyre.

"This is another method that could be added to the mix and it's cheap, effective and safe," she told AAP.

The vaccine is free for Australians aged 65 and over.

But Prof MacIntyre said a cost-effectiveness study should now investigate if it should be extended to people 50 and over - 50 being the start of the at-risk age group for heart attacks.

"The study should include the benefit of preventing heart attacks in a proportion of people," she said.

Heart disease is the leading cause of death in the world and carries an enormous cost burden.

Around 54,000 Australians suffer a heart attack every year and 8611 died from a heart attack in 2013.

The UNSW researchers conducted a systematic review and meta-analysis of 16 international case control studies to estimate the association of influenza and vaccination with heart attacks.

It confirmed their 2013 study which found the jab could lower the risk of a heart attack by 45 per cent.

They also found a strong link between the flu and heart attacks.

"If you have had influenza your risk of heart attack is doubled in the immediate time frame after having it," Prof MacIntyre said.

Previous research indicates that infections such as the flu might encourage blood to thicken or prompt an inflammatory response in arteries that are already diseased, and trigger a blockage in a partially blocked artery.

"Even if you're a healthy weight and you've no family history of heart attacks, you may have some thickening of your arteries without knowing it," she said.

"Based on this study's findings, I would recommend the flu jab for anyone over 50 regardless if they are at risk of heart disease."