AHA 2024: Email Reminders Improve Flu Shot Rates, Particularly Among Heart Attack Survivors

New research findings presented at the American Heart Association (AHA) Scientific Sessions 2024 demonstrate that using emails to encourage patients to get a flu vaccine improved vaccination rates, particularly among individuals with a history of heart attack.¹

Annual flu vaccination is recommended by both the AHA and CDC for nearly everyone 6 months of age and older, including individuals with heart disease. Influenza vaccination prevents the flu and its related complications and has also been shown to reduce major cardiovascular health problems in individuals who have survived a prior heart attack.¹

Woman reading an email on her phone | Image credit: © oatawa | stock.adobe.com

“Yearly influenza vaccines help prevent influenza infection and, in patients with a heart attack, are potentially cardioprotective,” said lead author Ankeet Bhatt, MD, MBA, ScM, a cardiologist at Kaiser Permanente San Francisco Medical Center, in a news release. “However, there are large gaps in implementing this effective therapy, and novel, scalable strategies to improve flu vaccination rates are needed.”¹

According to a meta-analysis published in the European Journal of Preventive Cardiology, researchers searched all electronic databases from inception until April15, 2022. Primary clinical outcomes were all-cause mortality and major adverse clinical events (MACEs). Secondary end points were heart failure, myocardial infarction, cardiovascular mortality, and stroke.²

Five randomized trials and 13 observational studies were included with a total of 22,532,165 patients, including 217,072 participants in the high cardiovascular risk or established cardiovascular disease population (vaccinated n=111,073). The mean age was 68 years, without any difference between groups.²

At a mean follow-up of 1.5 years, the vaccinated group was associated with a lower risk of all-cause mortality, MACE, cardiovascular mortality, and myocardial infarction, compared with the unvaccinated group. However, the incidence of stroke and heart failure did not differ between the 2 groups.²

Despite these positive data, flu vaccination rates often remain low. In Denmark, where the study presented at AHA took place, authors noted that about 80% of older adults get flu shots whereas only about 40% of younger adults with chronic diseases get flu shots.1 In the US, during the 2023-2024 flu season, about 45% of adults and 55% of children received at least 1 dose of a flu vaccine, according to CDC data.³

Study authors evaluated whether email-based reminders would improve vaccine use in a broad population, including older adults and individuals with chronic conditions during 2 recent flu seasons in Denmark. To do this, they conducted 3 national clinical trials during the 2022-2023 and 2023-2024 flu seasons: NUDGE-FLU, NUDGE-FLU-2, and NUDGE-FLU CHRONIC. Each trial assessed a series of behavioral science-informed nudges, delivered via a governmental email or letter system.¹

Participants were randomly selected to receive either 1 of the email letters encouraging flu vaccination or no reminder/standard of care. An email explaining the potential cardiovascular benefits of flu shots was more effective at increasing vaccination rates, according to the authors.¹

Investigators found that compared with usual care, individuals who received any of the nudge emails had higher rates of vaccination, with an improvement of 1.8% among heart attack survivors and 1.3% among adults without a history of heart attack. A message explaining the potential cardiovascular benefits of flu shots was more effective, demonstrating a 3.9% increase in vaccination among individuals with a history of heart attack and a 2% increase in those without.¹

Furthermore, among heart attack survivors, an email focused on cardiovascular benefits was even more successful among individuals who had not received a flu shot during the previous season. Individuals in this subcategory had a flu vaccine improvement rate of nearly 14% compared with an improvement in heart attack survivors who were previously vaccinated of only about 1.5%.¹

Finally, in the NUDGE-FLU-CHRONIC trial, the email highlighting cardiovascular benefits was even more effective among younger adults who survived a recent heart attack compared with those who had not, at 26% and 14% increases, respectively.¹

“These particularly important groups, those not previously vaccinated and those with a recent heart attack, may represent groups with the greatest cardiovascular protection to gain from vaccination,” Bhatt said in the news release.¹

One limitation of the research is that it is based solely on prespecified, secondary analysis across the trials, so the studies themselves were not solely dedicated to answering this question alone. In addition, researchers noted that particularly among older adults, flu vaccination rates in Denmark were high and vaccination rates may be much lower in other parts of the world. Further studies should examine whether that changes the effectiveness of this nudge strategy in populations with lower vaccination rates.¹

Despite these limitations, the encouraging results suggest this low-cost, scalable strategy should be considered for population-level outreach globally to improve flu vaccination rates, particularly if it is validated in other global health care contexts.

“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.”¹

REFERENCES

1. Email reminders improved flu shot rates in Denmark, notably among heart attack survivors. News release. American Heart Association. November 17, 2024. Accessed November 18, 2024. https://newsroom.heart.org/news/email-reminders-improved-flu-shot-rates-in-denmark-notably-among-heart-attack-survivors?preview=9757&preview_mode=True

2. Jaiswal V, Ang SP, Yaqoob S, et al. Cardioprotective effects of influenza vaccination among patients with established cardiovascular disease or at high risk cardiovascular risk: a systematic review and meta-analysis. Eur J Prev Cardiol. 2022;29(14):1881-1892. doi:10.1093/eurjpc/zwac152

3. Flu Vaccination Coverage, United States, 2023-24 Influenza Season. CDC. September 20, 2024. Accessed November 18, 2024. https://www.cdc.gov/fluvaxview/coverage-by-season/2023-2024.html