Adults vaccinated against flu at lower risk for heart complications, study finds

April 29 (UPI) -- Older adults who obtain a flu shot are less likely to suffer a heart attack or stroke and are at lower risk for death from heart-related health events in the year after getting vaccinated, an analysis published Friday found.

Just under 4% of older adults vaccinated against the seasonal virus experienced a "cardiovascular event" within the next year compared to just over 5% of those who did not receive the shot, data published Friday by JAMA Network Open showed.

Those who received the shot, which is offered annually, were 45% less likely to have had a recent diagnosis of acute coronary syndrome, or decreased blood flow in the coronary arteries that disrupts function in part of the heart muscle, the researchers said.

Flu vaccine recipients also were 46% less likely to die from acute coronary syndrome compared to those who did not get the shot, according to the researchers.

Fewer than 2% of flu vaccine recipients in the study died from cardiovascular-related causes, while about 3% who did not get the shot did, the data showed.

"In preventing and/or reducing severity of infection, vaccination also helps prevents downstream complications from flu infection, such as pneumonia, and further deterioration into cardiovascular events," study co-author Bahar Behrouzi told UPI in an email.

In addition, "some studies suggest that the vaccine itself may interact with the immune system and inflammatory processes to help stabilize plaques" that form in arteries and lead to the development of heart disease, said Behrouzi, a doctoral candidate in epidemiology at the University of Toronto in Canada.

The influenza vaccine, or flu shot, is developed annually based on predictions of what virus strains will be in circulating during the upcoming winter season, according to the Centers for Disease Control and Prevention.

In winter 2020-21, about 60% of people eligible to receive the vaccine nationally -- anyone age 6 months and older -- did so, the agency estimates.

However, that was not a typical year, given that the COVID-19 pandemic was at its peak and public health officials were urging people to get vaccinated against the flu to prevent a surge in cases of the seasonal virus.

Depending on the year, the vaccine is between 40% and 60% effective at protecting against development of symptoms or severe illness following flu infection, according to the agency.

For this study, Behrouzi and her colleagues analyzed data from six studies that collectively included more than 9,000 participants, most of whom were in their 60s.

"The take-home message [of our study] is to get the seasonal flu vaccine, especially if you have pre-existing cardiovascular disease, and even more so if it's recent acute coronary syndrome," Behrouzi said.

"Flu vaccine uptake tends to be low, perhaps especially among the people who stand to benefit from it the most, hence our hope with the results of this study is that they continue to build confidence in these vaccines," she said.