• Posted March 7, 2023

Highlighting Link Between Flu & Heart Trouble Can Nudge Folks to Get Vaccine

Flu kills more than 500,000 people globally each year and leads to heart problems for many others. Publicizing those potential cardiac ills may spur folks to get their annual flu vaccine, researchers say.

Danish researchers who studied vaccination messaging methods said the two best ways to get people to roll up their sleeves were either a simple reminder or by noting the link between contracting the flu and future heart problems.

"As cardiologists, it's very interesting that just telling people that we can also prevent other downstream issues like cardiovascular outcomes was what worked the best of all the nudge strategies -- even better than the reminder, which we expected would be positive,"said study leader Dr. Tor Biering-Sørensen. He is a professor in the Center for Translational Cardiology and Pragmatic Randomized Trials at Copenhagen University Hospital.

"A lot of studies have shown that people who get the flu vaccine have a lower risk of cardiovascular outcomes, and there may be protective effects [for the heart] that are not specific to flu infection," Biering-Sørensen continued in a news release. "The flu vaccine may have broader benefits that we don't yet know."

The research involved nearly 965,000 Danish citizens aged 65 and older. Half received one of nine different electronic letters recommending a flu shot while the other half got no message.

The other messages, which included a clear recommendation from a leading health authority to get vaccinated, did not result in a greater number of shots, the investigators found.

The goal was to influence vaccinations by Jan. 1, the ideal time to ensure protection, according to the researchers, though vaccinations can continue throughout the flu season.

The vaccination rate was found to be higher in people who received a letter about heart benefit than in those who received no letter: 81% compared to 80%. For the simple reminder, vaccination was 80.85% compared to 80.12% for no letter.

The heart message had a greater increase in vaccine uptake among the participants who had not been vaccinated for influenza in the prior season.

Biering-Sørensen thinks these increases in flu vaccine uptake might have been even more pronounced in countries where vaccination rates are low. In the United States, for example, only 49% of U.S. adults got a flu shot in the 2021-2022 influenza season, whereas about 80% of Danes get their shot.

An annual flu shot is widely recommended to help prevent infection, lessen illness severity and reduce complications.

"Figuring out ways to increase the percentage of people who get the flu [shot] and other vaccines is important,"Biering-Sørensen said. "Vaccines help prevent infectious diseases and for flu, specifically, many countries lag well behind the [World Health Organization] recommendation for over 75% of the population to be vaccinated."

The flu vaccine is free in Demark, so results could be different if cost were a barrier, the study authors noted.

The study was presented at a recent meeting of the American College of Cardiology and the World Heart Federation, in New Orleans. It was also published online March 5 in The Lancet. A pre-specified trial analysis was published online in the journal Circulation.

The study was funded by Sanofi, which makes flu vaccines.

More information

The U.S. Centers for Disease Control and Prevention has more on flu vaccines.

SOURCE: American College of Cardiology, news release, May 3, 2023