NUDGE-FLU Analysis Finds History of Heart Attack Increases Effectiveness of CV Gain Frame Letter

Ankeet Bhatt, MD, MBA, ScM
Credit: American Heart Association

New data from the landmark NUDGE-FLU program suggests patients with a history of myocardial infarction were more likely to receive a seasonal influenza vaccination after receiving an electronic message highlighting the cardiovascular benefits of flu shots.

Coming more than 2 years after the original NUDGE-FLU trial was presented at ACC.22, the latest study, which included data from more than 2 million patients randomized across 2 flu seasons, found use of the cardiovascular benefits “nudge” was associated with a 1.8% improvement in vaccination rates among heart attack survivors and a 1.3% improvement in rates among adults without a history of heart attack.

“Yearly influenza vaccines help prevent influenza infection and, in patients with a heart attack, are potentially cardioprotective,” said the study’s lead author Ankeet Bhatt, MD, MBA, SCM, a cardiologist at Kaiser Permanente San Francisco Medical Center, a research scientist at the Kaiser Permanente Northern California Division of Research, and an adjunct professor at the Stanford University School of Medicine. “However, there are large gaps in implementing this effective therapy, and novel, scalable strategies to improve flu vaccination rates are needed.”

A revolutionary trial program leveraging behavioral science-informed nudges, delivered via a governmental electronic email/letter system to improve vaccination rates, the NUDGE-FLU program has captivated trialists and the medical community since its initial release. Presented at the American Heart Association (AHA) Annual Scientific Sessions 2024, the current analysis included all 3 trials from the program—the NUDGE-FLU, NUDGE-FLU-2, and NUDGE-FLU CHRONIC trials, which were conducted during the 2022-2023 and 2023-2024 influenza seasons.

The original NUDGE-FLU trial was conducted during the 2022-2023 influenza season and randomized 964,870 adults aged 65 years and older to 1 of 9 different behavioral science-informed letters or usual care. NUDGE-FLU-2 was conducted during the 2023-2024 influenza season and randomized 881,373 adults aged 65 years and older to 1 of 6 different behavioral science-informed letters or usual care. NUDGE-FLU-CHRONIC was conducted during the 2023-2024 influenza season and randomized 299,881 adults aged 18 to 64 years with a chronic condition to 1 of 6 different behavioral science-informed letters or usual care.

Across the 3 trials, 2,146,124 patients underwent randomization. Of these, 2.8% (n=59,458) had a history of acute myocardial infarction.

Initial analysis revealed improvement in vaccine uptake was comparable in those with vs. without a history of acute myocardial infarction who received any nudge letter compared with usual care (+1.81 vs +1.32 percentage points; P for interaction = .09). Further analysis found receipt of the letter highlighting cardiovascular benefits of vaccination resulted in greater improvements in vaccine uptake among patients with a history of acute myocardial infarction relative to their counterparts without (+3.91 vs +2.03 percentage points; P for interaction = .002).

Additionally, investigators pointed out the cardiovascular benefits communications were greater in those who had not received a vaccination in the prior season (+13.7 vs +1.48 percentage points; P for interaction <.001). Investigators also called attention to differences among participants based on time since event, with a more pronounced effective observed in patients with more recent acute myocardial infarction (P for interaction <.001).

“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. “Notably, this strategy alone did not close all implementation gaps for flu vaccination. Other strategies in addition to messaging-based intervention need to be tested to fully close this important prevention gap in at-risk patients.”

References:

1. Bhatt AS. Electronic Nudges to Increase Influenza Vaccination among Patients with History of Myocardial Infarction: Insights from 3 Randomized Clinical Trials Enrolling >2 Million Patients. Paper presented at: American Heart Association Scientific Sessions 2024; November 15 - 18; Chicago, Il. Accessed November 16, 2024.
2. American Heart Association. Email reminders improved flu shot rates in Denmark, notably among heart attack survivors. American Heart Association Newsroom. November 11, 2024. Accessed November 17, 2024. https://newsroom.heart.org/news/email-reminders-improved-flu-shot-rates-in-denmark-notably-among-heart-attack-survivors.