Electronic nudges about potential heart benefits of flu vaccine boosted uptake
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NEW ORLEANS — Electronic nudges and reminders highlighting the potential CV benefits of influenza vaccination led to a modest uptake in vaccination rates among older adults in Denmark, according to results of the NUDGE-FLU trial.
“Influenza vaccination rates remain suboptimal despite known effectiveness against influenza infection and related complications including cardiovascular events. Prior reports indicate vaccine uptake is reported to be 50% to 70% in CVD groups,” Niklas Dyrby Johansen, MD, with Herlev and Gentofte Hospital in Copenhagen, Denmark, said during a late-breaking clinical trial presentation at the American College of Cardiology Scientific Session.
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The researchers looked at whether behavioral nudging would be a viable strategy to boost vaccination update on a population level. More than 964,000 individuals aged 65 years and older (mean age, 74 years; 51% women) in Denmark were randomly assigned to one of nine electronic letters or usual care, which was standard annual correspondence about influenza vaccination from the Danish Health Authority. Communications were delivered before the 2022-2023 influenza season via the country’s governmental electronic letter system.
The electronic letters featured different messages, ranging from a basic letter without name personalization to one highlighting the potential CV benefits of the influenza vaccine such as protection against MI, HF and other CVDs to a recommendation from a leading health authority to a loss-framing note emphasizing that low uptake places individuals and their loved ones at risk.
The results were simultaneously published in The Lancet.
Some nudges increased vaccine rates
Subsequent influenza vaccine uptake was higher in two groups: those who received the electronic letter highlighting the potential CV benefits (81% vs. 80.12%; P < .0001) and those who received a reminder letter 2 weeks after the first (80.85% vs. 80.12%; P = .0006).
“The repeated letter strategy with an additional reminder letter 14 days later significantly increased the influenza vaccination rate by 0.73% [and] also the cardiovascular gain letter informing on the potential cardiovascular benefits of vaccination also significantly increased influenza vaccination rates by 0.89%,” Johansen said.
Seventy-seven percent of individuals had received an influenza vaccine for the prior 2021-2022 influenza season. The researchers found that the CV benefits letter was particularly effective for individuals who did not receive an influenza vaccine during the prior (P = .0002).
The findings were also consistent in patients with and without CVD, according to the researchers.
Twenty-seven percent of individuals in this study had CVD.
During follow-up, 83% of those with CVD compared with 79.2% without CVD received the influenza vaccine (P < .001), according to a prespecified analysis published in Circulation.
As in the main trial, influenza vaccine uptake was higher in those who received the letter highlighting potential CV benefits and the reminder letter compared with usual care, regardless of the presence or absence of CVD. The effect of the nudges on vaccine uptake was consistent across major CVD subgroups, including HF, ischemic heart disease and atrial fibrillation, according to the results.
None of the other nudging strategies were effective, overall or by CVD status, and none of the interventions had a negative effect on vaccination rates, Johansen said.
Global rates ‘remain suboptimal’
Global vaccination rates “remain suboptimal,” likely due to knowledge gaps, preexisting beliefs around vaccination, concerns of safety and other factors that promote vaccine hesitancy, the researchers wrote in The Lancet.
Denmark has one of the highest influenza vaccine rates in the world, at more than 80%, according to Tor Biering-Sørensen, MD, MSc, MPH, PhD, professor in the Center for Translational Cardiology and Pragmatic Randomized Trials, Copenhagen University Hospital, Hellerup. In the United States, patients with HF, for example, have vaccine coverage rates of 50% to 70%, according to the researchers. Rates are generally similar or lower in other high-income countries, they wrote in Circulation.
Johansen said the absolute effect of the electronic nudges may have been larger in a population with a lower vaccination rate than Denmark.
“When applied to other global settings — eg, among the approximately 63 million Medicare beneficiaries in the USA — a 0.89% absolute increase in vaccination rate achieved through the most successful electronic letter in NUDGE-FLU would be expected to lead to an excess of 500,000 additional vaccinations. Extrapolating from the U.S. Centers for Disease Control and Prevention’s estimates of outcomes prevented by influenza vaccination in U.S. adults aged 65 years or older during the 2019-2020 season at a vaccination rate of 69.8%, a 0.89% absolute increase in vaccination rate accomplished by an electronic letter would result in an additional 7,849 illnesses, 4,395 medical visits, 714 hospitalization and 66 deaths prevented yearly,” the researchers wrote in The Lancet.
“The concept that the nudges plant an idea that leads to an action is pretty much the basis of a lot of these health care interventions, which seems like a small way to have a big impact in outcome.” David Cho, MD, MBA, FACC, chair of the ACC Health Care Innovation Council and cardiologist at UCLA Health, said during a discussion of the trial at a press conference.
“Despite the modest effect sizes [in NUDGE-FLU], the results may have important implications when translated to a population level,” Biering-Sørensen said during the press conference.
References:
- Johansen ND, et al. Lancet. 2023;doi:10.1016/S0140-6736(23)00453-1.
- Modin D, et al. Circulation. 2023;doi:10.1161/CIRCULATIONAHA.123.064270.
Perspective
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Robert A. Harrington, MD, FAHA
This is a very interesting study. We did something in our health system a few years ago that was very similar to try to nudge people with different types of contact. That was a localized health system, but this is a much bigger effort. You can’t do a countrywide effort everywhere, but in certain health systems, you can. The sheer scope was impressive.
Also impressive was the different types of behavioral nudges, and that the researchers actually got a result that showed that something might be effective.
Perhaps not surprisingly, giving people insight into flu vaccine lowering direct risk for CVD was one of the winners. For cardiologists, that felt good. I thought the social-good option might win, given the perception of Scandinavian countries placing a priority on doing things for the social good.
Not surprising from a human behavior perspective is that if you do something repeatedly, you increase the yield.
This is actionable. In the U.S., it may be hard to get this at the national level, but we can get it at the county level. It would be nice to see something like this rolled out in counties across the U.S. I could also see individual health systems doing this. I get texts from my county about road closures; why couldn’t I also get one reminding me to get my flu shot?
The one caution is that Danes are more ethnically homogenous in terms of racial backgrounds, experiences, socioeconomics, etc, than we are in the U.S. It would be nice to see more data across difference racial and socioeconomic subgroups, because of the hypothesis that different behavioral nudges may work in different groups.
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Johansen ND, et al. Late-Breaking Clinical Trials III. Presented at: American College of Cardiology Scientific Session; March 4-6, 2023; New Orleans (hybrid meeting).
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