Email Reminders Boost Flu Vaccination Rates in Denmark, Especially Among Heart Attack Survivors

A series of clinical trials in Denmark has demonstrated the effectiveness of email reminders in increasing influenza vaccination rates, with particularly notable improvements among heart attack survivors. The research, presented at the American Heart Association's Scientific Sessions 2024 and published in JAMA Cardiology, offers promising insights into strategies for boosting flu shot uptake across diverse populations.

The study, led by Dr. Ankeet Bhatt of Kaiser Permanente San Francisco Medical Center, involved more than 2 million Danish adults across three national clinical trials conducted during the 2022-2023 and 2023-2024 flu seasons. Researchers tested various electronic messages, or 'nudges,' delivered through a governmental email system to encourage flu vaccination.

Results showed that compared to usual care, participants receiving any of the email nudges had higher vaccination rates. However, the most effective message was one that explained the potential cardiovascular benefits of flu shots. This approach led to a 3.9% increase in vaccination among people with a history of heart attack, compared to a 2% increase for those without such history.

The impact was even more pronounced among certain subgroups. Heart attack survivors who were not vaccinated in the previous flu season showed a remarkable 14% improvement in vaccination rates when receiving the cardiovascular-focused message. Additionally, younger adults with a recent heart attack demonstrated a 26% increase in vaccination rates in response to this targeted messaging.

These findings are particularly significant given the importance of flu vaccination for cardiovascular health. Both the American Heart Association and the U.S. Centers for Disease Control and Prevention recommend annual flu shots for nearly all individuals, with special emphasis on those with heart disease. Flu vaccines not only prevent infection but have also been shown to reduce major cardiovascular events in people with a history of heart attacks.

The study's results suggest that this low-cost, easily scalable strategy could be implemented globally to improve flu vaccination rates across healthcare systems. Dr. Bhatt noted that while the approach was effective, it did not completely close the implementation gap for flu vaccination, indicating that additional strategies may be necessary to fully address this preventive care issue.

While the research shows promise, it's important to note some limitations. The analysis was based on a prespecified, secondary examination across the trials, and the high baseline vaccination rates among older adults in Denmark may not be representative of other global populations. Further validation studies are already underway in the United States to assess the strategy's effectiveness in different healthcare contexts.

As healthcare systems worldwide continue to grapple with suboptimal vaccination rates, particularly among high-risk groups, this research offers a practical and potentially impactful solution. By leveraging targeted electronic communications to highlight the cardiovascular benefits of flu shots, healthcare providers and policymakers may be able to significantly improve vaccination rates and, consequently, reduce the burden of both influenza and cardiovascular events.