Flu Shots Could Reduce Heart Attacks by 10% When Hospitalized

Only 3 percent of in-patients had a heart attack or unstable angina after receiving an influenza vaccination

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There’s now another reason to get your yearly flu shot. A new study reported that in-patient influenza vaccination was associated with fewer subsequent heart attacks. 

The new study being presented at the American College of Cardiology’s 68th Annual Scientific Session on March 16, 2019, of nearly 30 million hospital records shows that people who got a flu shot while hospitalized had a 10 percent lower risk of having a heart attack during that year. 

This study is the largest to date to investigate the relationship between influenza vaccination and heart attacks. 

This new finding is consistent with previous research suggesting getting a flu vaccine can reduce a person’s risk of major cardiovascular problems. 

“You don’t need to be a medical professional to see this data and understand the importance of getting the flu vaccine,” said Mariam Khandaker, MD, internal medicine resident at Icahn School of Medicine at Mount Sinai St. Luke’s and Mount Sinai West and the study’s lead author.   

Drawing on a data set known as the National Inpatient Sample, these researchers analyzed the records of nearly 30 million adult patients who visited a hospital in the United States in 2014. 

About 2 percent of patients studied had received a flu shot while hospitalized and 98 percent had not (the data set did not include flu shots received outside of a hospital setting). 

Of those who had not received a flu vaccine, 4 percent had a heart attack or unstable angina. 

Of those who had gotten the flu shot, only 3 percent had a heart attack or unstable angina. 

This is a statistically significant difference due to the large size of the data set. 

In particular, the vaccinated patients had about 5,000 fewer cases of heart attacks that would have been expected without the vaccine. 

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After adjusting for several confounding variables, vaccination was associated with a 10 percent reduction in the risk of having a heart attack. 

Heart attacks and unstable angina occur when plaque breaks free from the lining of a blood vessel and creates a clog in one or more of the heart’s arteries, fully or partially blocking the flow of blood to the heart. 

Having the flu can cause inflammation in the blood vessels, which increases the likelihood that plaque will rupture. 

The flu can also cause physiological effects, such as decreased oxygen supply and increased heart rate, which can exacerbate existing heart conditions. 

“By getting the flu vaccine, you can help to prevent this cascade of events from taking place and, thus, prevent a heart attack,” Dr. Khandaker said. 

The Centers for Disease Control and Prevention (CDC) recommends everyone age 6 months and older gets a flu vaccine each year. The CDC estimates that only 37 percent of U.S. adults received the vaccine during the 2017–2018 flu season, the most recent year for which complete data are available. 

Dr. Khandaker said, “It is important for physicians to educate patients about the benefits of vaccination in order to help them make informed decisions. Hospitals are a good venue to do this, in addition to other places such as the primary care clinic.” 

Dr. Khandaker will present the study, “Influenza Vaccination and Prevalence of Myocardial Infarction: An Analysis of the 2014 U.S. National Inpatient Sample,” on Saturday, March 16, at 3:45 p.m. CT in the Acute and Stable Ischemic Heart Disease Moderated Poster Theater, Poster Hall, Hall F. 

The ACC’s Annual Scientific Session will take place March 16–18, 2019, in New Orleans. 

The mission of the College and its more than 52,000 members is to transform cardiovascular care and to improve heart health. For more, visit acc.org.