Flu Shots May Also Protect Heart

a person getting a vaccine
(Image credit: Dreamstime)

Getting a flu shot may reduce the risk of major heart problems, such as heart attacks or unexpected chest pain, particularly in people who have recently experienced such heart complications, a new review suggests.

Researchers analyzed information from five previously published studies in which more than 6,000 people, whose average age was 67, were randomly assigned to receive an influenza vaccination, a placebo or no treatment. About one-third of participants had a history of cardiovascular problems.

Among those who received flu shots, 95 people, or 2.9 percent, experienced a major cardiovascular problem over a one-year period. In contrast, among those who received a placebo or no treatment, 151 people, or 4.7 percent, experienced a major cardiovascular problem.

This translates to one major cardiovascular problem prevented for every 58 people who were vaccinated, the researchers said. [6 Flu Vaccine Myths]

The benefit of vaccination was more pronounced among patients who had recently experienced a cardiovascular problem caused by a sudden reduction of blood flow to the heart. Of these patients, about 10.25 percent of those who received flu shots experienced another cardiovascular problem in a one-year period, compared to 23.1 percent of those who received a placebo or no treatment.

In vulnerable patients, getting the flu may trigger the rupture of artery plaques, inflammation of the heart muscle, irregular heartbeats or other problems that could lead to heart injury, the researchers said. The findings suggest flu vaccination "represents a simple, once-annual protective therapy to reduce cardiovascular events," the researchers from the University of Toronto wrote in the Oct. 23 issue of the Journal of the American Medical Association.

However, the study found only an association, and cannot prove that flu shots actually prevent major cardiovascular problems. A large study conducted at multiple healthcare facilities is needed to confirm the results, the researchers said.

In an editorial accompanying the study, Dr. Kathleen Neuzil of the University of Washington School of Medicine said, "Regardless of whether influenza vaccine reduces cardiovascular disease, the known morbidity of influenza in older adults with and without high-risk conditions, and the known efficacy of the vaccine warrant its use."

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Rachael Rettner

Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.