Electronic Nudges Improved Flu Shot Uptake in Patients With Acute MI History

CHICAGO — Electronic nudges increased uptake of flu vaccines among patients with a history of acute myocardial infarction (MI), results from three Danish randomized trials showed.

Among over 2 million patients, a letter explaining the cardiovascular benefits of influenza vaccination led to larger improvements in vaccine uptake among patients with a history of acute MI versus those without (+3.91 vs +2.03 percentage points, P=0.002 for interaction by acute MI status), reported Ankeet Bhatt, MD, of the Kaiser Permanente San Francisco Medical Center & Division of Research, during the American Heart Association annual meeting.

The study was also published in JAMA Cardiology.

Improvement in vaccine uptake was similar between patients with and without a history of acute MI who received any nudge letter compared with usual care (+1.81 vs +1.32 percentage points, P=0.09 for interaction by acute MI status).

For the patients in the acute MI group, the benefits of the cardiovascular-focused letter — which included the phrase, “In addition to its protection against influenza infection, vaccination also seems to protect against cardiovascular disease such as heart attacks and heart failure” — were more pronounced in those not vaccinated in the prior season (+13.7 vs +1.48 percentage points, P<0.001 for interaction). Among younger patients with chronic disease, the cardiovascular-focused letter was especially effective in patients with a more recent acute MI (P<0.001 for interaction by continuous recency of acute MI).

The wording of the added phrase clearly resonated with people who had a history of MI, Bhatt said.

“Yearly influenza vaccines help prevent influenza infection and, in patients with a heart attack, are potentially cardioprotective,” he explained. “However, there are large gaps in implementing this effective therapy, and novel, scalable strategies to improve flu vaccination rates are needed.”

In Denmark, about 80% of older adults and 40% of younger adults with chronic diseases get flu shots, Bhatt noted. In a statement, the American Heart Association cited CDC statistics showing that about 45% of adults received the flu vaccine in the U.S. 2023-2024 flu season.

“The data suggest that cardiovascular-focused messaging was effective across a broad population; this strategy should be considered as part of a suite of strategies to improve cardiovascular prevention and encourage flu vaccination among high-risk patients, including those with a history of heart attack,” Bhatt said.

Commenting on the trial, Dipti Itchhaporia, MD, of the Hoag Heart and Vascular Institute in Newport Beach, California, and past president of the American College of Cardiology, told MedPage Today that “we can see from these trials that electronic nudges do increase influenza vaccination rates, especially among the individuals who are most at risk — those who have already had one heart attack.”

The question in the current political landscape is whether a vaccination-adverse government leadership would support such a campaign, Itchhaporia noted. “However, it doesn’t have to be the government that does this. We could get together with industry — manufacturers, pharmacies, and various databases and registries, along with medical and educational societies, to do something similar as was done in Denmark in these clinical trials.”

This pooled analysis included data from the NUDGE-FLU, NUDGE-FLU-2, and NUDGE-FLU-CHRONIC trials in Denmark. They were conducted during the 2022-2023 and 2023-2024 influenza seasons.

The 2,146,124 participants were randomized to usual care or various behaviorally informed, electronically delivered, letter-based nudges. Mean participant age was 71.1, and 51.9% were women. Across the three studies, 2.8% of participants had a history of acute MI.

Vaccinations were provided free of charge.

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