Background: Influenza vaccination is associated with reduced risk of all-cause mortality in patients with diabetes mellitus (DM). However, vaccination rates remain suboptimal.

Methods: NUDGE-FLU was a nationwide, pragmatic implementation trial among Danish citizens ≥65 years during the 2022/23 influenza season. Households were randomized in a 9:1:1:1:1:1:1:1:1:1 ratio to usual care or 9 different electronic nudge letters. Baseline and outcome data were obtained via nationwide registries. The endpoint was receipt of a seasonal influenza vaccine before Jan. 1, 2023. In this pre-specified sub-study, effect modification by DM status was assessed in a pooled analysis of all intervention arms vs. usual care, and for individual letters.

Results: Of 964,870 participants from 691,820 households, 123,974 had DM. During follow-up, 84.2% with DM vs. 81.5% without DM received a vaccine (p<0.001). In the pooled analysis, DM status modified the effect of any electronic letter compared with usual care on vaccine uptake (p=0.030) such that the effect of any letter was attenuated in participants with DM (82.7% vs. 83.0%; difference, -0.23 percentage points; 99.55%CI: -0.94-0.48; p=0.37) vs. without DM (80.0% vs. 79.7%; difference, +0.36 percentage points; (0.07-0.66); p<0.001). In NUDGE-FLU, 2 of the 9 letters (one emphasizing potential cardiovascular benefits of vaccination and a repeated letter) significantly increased vaccine uptake vs. usual care. Point estimates suggested benefits were more pronounced in participants without DM, but no significant interactions were observed in either case (p>0.10).

Conclusion: In a pooled analysis, the effect of any electronic nudge was moderately albeit significantly greater in participants without DM. These findings further suggest that the beneficial effects of specific nudges, including repeated messaging and emphasizing cardiovascular benefits, may be more pronounced in participants without DM.


M. C. H. Lassen: None. J. S. Jensen: None. C. Martel: None. P. Valentiner-branth: None. T. Biering-sørensen: Advisory Panel; Sanofi, Amgen Inc., GlaxoSmithKline plc., Research Support; Sanofi, Amgen Inc., Boston Scientific Corporation, Novo Nordisk, AstraZeneca, Speaker's Bureau; Sanofi, GlaxoSmithKline plc. N. Johansen: None. M. Vaduganathan: Advisory Panel; American Regent, Amgen, AstraZeneca, Bayer AG, Baxter Healthcare, Boehringer Ingelheim, Chiesi, Cytokinetics, Lexicon Pharmaceuticals, Novartis, Novo Nordisk, Pharmacosmos, Relypsa, Roche Diagnostics,, Research Support; American Regent, Amgen, AstraZeneca, Boehringer Ingelheim, Bayer AG, Galmed, Novartis, Bayer AG, Occlutech, Impulse Dynamics, and Roche Diagnostics, Speaker's Bureau; AstraZeneca, Boehringer Ingelheim, Cytokinetics, Novartis, Roche Diagnostics. A. Bhatt: None. D. Midin: None. B. Claggett: Consultant; Corvia, Cardurion, Cytokinetics Inc., Novartis, Intellia. S. I. Samson: Employee; Sanofi. M. Loiacono: Employee; Sanofi. P. Sivapalan: None.



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