A new analysis of the NUDGE-FLU trial program reveals that email reminders can effectively encourage patients with a history of acute myocardial infarction (MI) to receive their annual influenza vaccination. The study, presented at the American Heart Association 2024 Scientific Sessions, found that targeted messaging emphasizing the protective effects of vaccination on cardiovascular (CV) health was particularly impactful, especially among those hesitant to get vaccinated and younger patients with more recent MIs.
Ankeet S. Bhatt, MD (Kaiser Permanente San Francisco Medical Center, CA), highlighted the increased risk of cardiovascular events, including acute MI, associated with influenza. He referenced the 2021 IAMI trial, which demonstrated that flu shots could reduce this added risk in post-MI patients, leading to strong recommendations for influenza vaccination in cardiovascular guidelines. Despite these recommendations, vaccination rates in this high-risk group remain suboptimal, underscoring the need for effective strategies to improve uptake.
The NUDGE-FLU trials, conducted in Denmark, utilized the government email system to send electronic reminders to participants, prompting them to get vaccinated against influenza. Orly Vardeny, PharmD (Minneapolis VA Health Care System, MN), emphasized the significant burden of influenza in the United States, citing CDC data from the 2023-2024 season, which reported 34 million symptomatic illnesses, 15 million medical visits, over 380,000 hospitalizations, and 17,000 deaths. Nearly half of those hospitalized had cardiovascular disease.
Impact of Targeted Messaging
The pooled analysis included data from NUDGE-FLU (2022-2023 season; patients aged ≥ 65 years), NUDGE-FLU-2 (2023-2024 season; patients aged ≥ 65 years), and NUDGE-FLU-CHRONIC (2023-2024 season; patients aged 18-64 with a chronic condition). The intervention involved delivering behavioral science-informed letters electronically. Of the over 2.1 million participants, 59,458 (3.8%) had a history of acute MI.
While overall vaccine uptake improved with any reminder letter, the effect was more pronounced when patients received a letter specifically highlighting the cardiovascular benefits of vaccination. In this group, those with a history of acute MI were significantly more likely to get a flu shot compared to those without such a history (+3.91 vs +2.03 percentage points; P for interaction = 0.002). This targeted nudge involved adding a single sentence to the standard letter, emphasizing the flu shot's ability to reduce the risk of MI and heart failure.
Considerations for US Implementation
Despite the promising results, experts caution against directly generalizing these findings to the United States. Mohammad Madjid, MD (University of California, Los Angeles), and Payam Safavi-Naeini, MD (Texas Heart Institute, Houston, TX), noted that lower flu vaccination rates in the US, particularly among adults aged 18 to 64, may stem from differences in healthcare systems and health awareness.
They also highlighted the challenges of vaccine hesitancy, exacerbated by social media misinformation, as a significant barrier to improving vaccination rates in the US. A coordinated effort involving private and governmental sectors, physicians, pharmacists, nurses, and other healthcare professionals is needed to overcome these barriers.
Bhatt acknowledged the unique aspects of the Danish healthcare system, such as free flu shots and a nationwide vaccination registry, but suggested that aspects of the intervention could be adapted in the US through large healthcare delivery systems and electronic health records. However, he stressed the importance of validation studies in the US to address the pervasive implementation gaps in influenza vaccination, given the strong feelings surrounding vaccination in the country.
