The risk of heart attack — or myocardial infarction — is particularly acute in older adults, said the report in the New England of Medicine.
“Our findings are important because an association between influenza and acute myocardial infarction reinforces the importance of vaccination,” said lead author Jeff Kwong, a scientist at the Institute for Clinical Evaluative Sciences and Public Health Ontario.
The study was based on nearly 20,000 adult cases of laboratory-confirmed influenza infection in Ontario, Canada from 2009 to 2014.
Of those, 332 patients were hospitalized for a heart attack within one year of their flu infection.
The risk appeared highest in the first week, particularly for older people, those with influenza B infections, and patients experiencing their first heart attack.
Other respiratory viruses were also seen to raise the risk of heart attack, though not as much as the flu.
Previous studies have also pointed to a link between the flu and cardiac crises and death.
Kwong urged new “international guidelines that advocate for influenza immunization in those at high risk of a heart attack.”
He also called on people at risk of heart disease to “take precautions to prevent respiratory infections, and especially influenza, through measures including vaccinations and hand washing.”