The electronic letters were sent out Sept. 16, 2022, and the primary endpoint was vaccine receipt on or before Jan. 1, 2023.
All individuals received an informative vaccination encouragement letter from the Danish Health Authority (usual care) delivered via the same electronic letter system during Sept. 17 through Sept. 21, 2022.
The individuals had a mean age of 73.8 years, 51.5% were women, and 27.4% had chronic cardiovascular disease.
The analyses were done in one randomly selected individual per household.
Influenza vaccination rates were significantly higher in the cardiovascular gain–framing nudge group vs. usual care (81.00% vs. 80.12%; difference, 0.89 percentage points; P < .0001) and in the repeat-letter group vs. usual care (80.85% vs 80.12%; difference, 0.73 percentage points; P = .0006).
These two strategies also improved vaccination rates across major subgroups.
The cardiovascular gain–framed letter was particularly effective among participants who had not been vaccinated for influenza in the previous season.
The seven other letter strategies did not increase flu shot uptake.
Subanalysis in CVD
In the prespecified subanalysis of the NUDGE-FLU trial of patients aged 65 and older that focused on patients with CVD, Daniel Modin, MB, and colleagues report that 83.1% of patients with CVD vs. 79.2% of patients without CVD received influenza vaccination within the requested time (P < .0001).
The two nudging strategies – a letter highlighting potential cardiovascular benefits of influenza vaccination or a repeat letter – that were effective in boosting flu shot rates in the main analysis were also effective in all major CVD subgroups (ischemic heart disease, pulmonary heart disease, heart failure, atrial fibrillation, cerebrovascular disease, atherosclerotic CVD, embolic or thrombotic disease, and congenital heart disease).
Despite strong guideline endorsement, “influenza vaccination rates remain suboptimal in patients with high-risk cardiovascular disease,” Dr. Morin and colleagues write, possibly because of “insufficient knowledge among patients and providers of potential clinical benefits, concerns about vaccine safety, and other forms of vaccine hesitancy.”
Their findings suggest that “select digital behaviorally informed nudges delivered in advance of vaccine availability might be utilized to increase influenza vaccinate uptake in individuals with cardiovascular disease.”
NUDGE-HF was funded by Sanofi. Dr. Johansen and Dr. Modin have no disclosures. The disclosures of the other authors are listed with the articles. Dr. Stockwell has no disclosures.
A version of this article first appeared on Medscape.com.