A series of clinical trials in Denmark has demonstrated the effectiveness of electronic reminders in increasing influenza vaccination rates, with particularly strong results 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 improving public health strategies.
The study, led by Dr. Ankeet Bhatt of Kaiser Permanente San Francisco Medical Center, involved over 2 million Danish adults across three national clinical trials during the 2022-2023 and 2023-2024 flu seasons. Participants were randomly selected to receive email reminders about flu vaccination or no reminder at all.
Results showed that compared to usual care, those who received any type of email reminder had higher vaccination rates, with a 1.8% increase among heart attack survivors and a 1.3% increase in adults without a history of heart attack. However, the most effective message was one that explained the potential cardiovascular benefits of flu shots, leading 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, in one trial, younger adults with a recent heart attack demonstrated a 26% increase in vaccination rates when receiving this targeted message.
Dr. Bhatt emphasized the significance of these findings, stating that the data suggest 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.
The study's results are particularly relevant given the current vaccination rates. In Denmark, while about 80% of older adults get flu shots, only about 40% of younger adults with chronic diseases do so. In the United States, during the 2023-2024 flu season, about 45% of adults and 55% of children received at least one dose of the flu vaccine, according to the CDC.
The American Heart Association and the U.S. Centers for Disease Control and Prevention recommend annual flu vaccination for nearly all people ages 6 months and older, including those with heart disease, with rare exceptions. Flu shots are crucial not only in preventing influenza and its complications but have also been shown to reduce major cardiovascular health problems in people with a prior heart attack.
While the study demonstrates the potential of this low-cost, scalable strategy, Dr. Bhatt noted that it alone did not close all implementation gaps for flu vaccination. He suggested that additional strategies need to be tested to fully address this important prevention gap in at-risk patients.
The research does have limitations, including being based on a prespecified, secondary analysis across the trials. Additionally, the high vaccination rates among older adults in Denmark may not be representative of other parts of the world, necessitating further validation in different populations and healthcare contexts.
Despite these limitations, the study's findings offer valuable insights into improving public health strategies. As flu vaccination remains a critical tool in preventing illness and reducing cardiovascular risks, particularly among vulnerable populations, this research provides a promising avenue for increasing vaccination rates on a global scale.
