During a year where flu cases have broken records in the U.S. and flu vaccination is at a low, new research indicates that getting the vaccine could have a surprise side effect.
This side effect is actually a positive one, said authors of the research published in the BMC Public Health journal this month. They found that “influenza vaccination is associated with lower odds of myocardial infarction in observational studies.”
That means that they linked getting a flu shot with a decreased risk of heart attacks (known as myocardial infarctions, or MIs).
Just last month, data from the U.S. Centers for Disease Control and Prevention showed that flu-like activity in the U.S. had reached the highest level on record, per a CNN report. It said the health agency started tracking flu activity about 30 years ago.
Psychology Today also reported earlier this month that flu vaccination rates had hit a record low in the U.S., with 45% of children and 46% of adults vaccinated through January. As of last week, the CDC said seasonal influenza activity remained elevated nationwide and this week, the CDC said that an estimated 134.6 million doses have been distributed in the U.S. throughout the current flu season.
“Influenza (flu) vaccination has been shown to reduce the risk of flu and its potentially serious complications. There is still time to get vaccinated against flu this season,” said the CDC this week.
As for the association between influenza vaccination and the risk of MI, study authors said they conducted a “meta-epidemiological study,” using evidence from observational studies found in PubMed, Embase, and the Cochrane Library from inception to July 16, 2025. Overall, 15 studies (seven cohort studies, seven case-control studies, and one self-controlled case-series) involving more than 23 million individuals were included.
A review of these studies found that influenza vaccination was associated with lower odds of MI compared with no vaccination. According to the study authors, the association was consistent across study designs, age categories, and MI history.
A note on the online publication acknowledges that the research was unedited as of Wednesday and that a final publication “will undergo further editing.” Any errors included before final edits might affect the content.
“While causal inference cannot be established, these findings support the potential role of influenza vaccination in cardiovascular risk prevention and highlight the need for further well-designed studies to clarify the nature and durability of this association,” said the study authors.