An Australian study has found the flu vaccine can almost halve the chances of a heart attack for middle-aged people showing signs of heart disease.

Researchers from the School of Public Health at the University of New South Wales found the link after examining more than 500 patients at Westmead Hospital in Sydney's west.

Their findings have been published today in the international journal Heart.

The study was led by the head of the School of Public Health, Professor Raina MacIntyre.

"The flu vaccine reduces the risk of heart attack. It has a protective effect of (a) 45% reduction of the risk of heart attack.

"What we were able to do is compare the vaccination rates and the heart attack rates between people and measure vaccine effectiveness."

Professor MacIntrye says the findings add weight to arguments that the flu vaccine should be recommended for people over the age of 50, who are generally at a higher risk of suffering a heart attack.

"Previously the policy debate has looked at the cost effectiveness of lowering the age of vaccination below 65 to the age of 50, looking only at the cost of preventing influenza," Professor MacIntyre said.

"What this study shows is that, at least, policy makers should be also looking at the cost saving of preventing heart attack."

The influenza vaccine is currently free for people over 65 and those with specific chronic diseases, including heart disease.

Professor Mcintyre says the vaccine is significantly underused by those aged 50 to 64, and there would be much higher rates if the jab was recommended for everyone.

"Heart attack is the leading cause of death in Australia, and in the world in fact, so there is potentially a significant population health impact from a vaccine that can reduce the risk of heart attack," she said.