Having a bout of influenza is a serious condition and it’s creating havoc in your body, even if you are healthy. Australian research indicates that a recent influenza infection was an unrecognized comorbidity in almost 10% of hospital patients. Influenza did not predict an AMI (Acute Myocardial Infarction), but vaccination was significantly protective but underused.
The influenza vaccine can almost halve the chances of a heart attack for people aged 50 to 64, who are at risk for heart disease, according to the study.
Having a heart attack is the leading cause of death in the western world, which suggests that there is potentially a significant population health impact from a vaccine that can reduce the risk of heart attack. While being vaccinated against an infection of the influenza virus does not prevent all possible heart attacks, it does significantly reduce the chance of having one.
 MacIntyre et al: Ischaemic heart disease, influenza and influenza vaccination: a prospective case control study in Heart - 2013