Utilizing echocardiography and unsupervised machine learning for heart failure risk identification.

BACKGROUND: Global longitudinal strain (GLS) is recognized as a powerful predictor of heart failure (HF). However, the entire strain curve may entail important prognostic information regarding HF risk that might be undiscovered by only focusing on the peak strain value. OBJECTIVE: The hypothesis of the present study was, that analysis of the entire strain curve using unsupervised machine learning (uML) would reveal novel ventricular deformation patterns capable of predicting incident HF independently of GLS. METHODS: Longitudinal strain curves from 3710 subjects from the general population without prevalent HF were analyzed using uML. RESULTS: Mean age was 56 years and 43 % were male. During a median follow-up of 5.3 years, 92 subjects (2.5 %) developed HF. The uML algorithm generated a hierarchical clustering tree (HCT) resulting in 10 different clusters. Generally, the strain curves displayed reduced early diastolic strain to peak-strain ratio with an increasing incidence rate of HF. In multivariable Cox regressions, cluster 9 was significantly associated with increased risk of HF when compared to cluster 2-5, and 7-8 [For cluster 3: HR 8.95, 95 %CI: 2.08;38.48, P = 0.003] even though the subjects of cluster 9 were younger, displayed healthier clinical baseline characteristics, and only had slightly reduced GLS. The mean strain curve of cluster 9 displayed an early systolic lengthening followed by a late and reduced contraction specifically related to the basal lateral segment. CONCLUSION: The unsupervised machine learning algorithm identified unknown strain patterns beyond GLS presumably related to increased risk of HF.

Electronic Nudges to Increase Influenza Vaccination in Patients With Chronic Diseases: A Randomized Clinical Trial.

Importance: Despite strong worldwide guideline recommendations, influenza vaccination rates remain suboptimal among young and middle-aged patients with chronic diseases. Effective scalable strategies to increase vaccination are needed. Objective: To investigate whether electronically delivered letter-based nudges informed by behavioral science could increase influenza vaccination uptake among patients aged 18 to 64 years with chronic diseases. Design, Setting, and Participants: Nationwide pragmatic registry-based randomized clinical implementation trial conducted between September 24, 2023, and May 31, 2024, enrolling all Danish citizens aged 18 to 64 years who met criteria for free-of-charge influenza vaccination in light of preexisting chronic disease. All trial data were sourced from nationwide administrative health registries. Intervention: Randomized in 2.45:1:1:1:1:1:1 ratio to no letter (usual care) or 6 different behaviorally informed electronic letters. Main Outcomes and Measures: The primary end point was receipt of influenza vaccination on or before January 1, 2024, assessed in 7 prespecified coprimary comparisons (all intervention groups pooled vs usual care and each individual intervention group vs usual care). Absolute risk difference in proportions and a crude relative risk were calculated for each comparison. Results: A total of 299 881 participants (53.2% [159 454] female, median age, 52.0 [IQR, 39.8-59.0] years) were randomized. Compared with usual care, influenza vaccination rates were higher among those receiving any intervention letter (any intervention letter, 39.6% vs usual care, 27.9%; difference, 11.7 percentage points; 99.29% CI, 11.2-12.2 percentage points; P < .001). Each individual letter type significantly increased influenza vaccination with the largest effect sizes observed with a repeated letter sent 10 days after the initial letter (repeated letter, 41.8% vs usual care, 27.9%; difference, 13.9 percentage points; 99.29% CI, 13.1-14.7 percentage points; P < .001) and a letter emphasizing potential cardiovascular benefits of vaccination (cardiovascular gain, 39.8% vs usual care, 27.9%; difference, 11.9 percentage points; 99.29% CI, 11.1-12.7 percentage points; P < .001). Vaccination rates were improved across major subgroups. Conclusions and Relevance: In a nationwide randomized clinical implementation trial, electronically delivered letter-based nudges markedly increased influenza vaccination compared with usual care among young and middle-aged patients with chronic diseases. The results of this study suggest that simple, scalable, and cost-efficient electronic letter strategies may have substantial public health implications. Trial Registration: ClinicalTrials.gov Identifier: NCT06030739.

Excess Mortality and Hospitalizations Associated With Seasonal Influenza in Patients With Heart Failure.

BACKGROUND: Influenza virus may cause severe infection in patients with heart failure. It is known that influenza infection is associated with increased morbidity and mortality in patients with heart failure. However, less is known about the excess burden of morbidity and mortality caused by influenza infection in patients with heart failure at a population level. OBJECTIVES: The purpose of this study was to estimate the excess burden of morbidity and mortality as determined by annual excess number of deaths and hospitalizations associated with influenza infection in patients with heart failure in Denmark. METHODS: We collected nationwide data on weekly number of deaths and hospitalizations among patients with heart failure in Denmark and weekly estimates of influenza circulation as determined by the proportion of positive influenza samples analyzed at all Danish Hospitals. These data were correlated in a time series linear regression model, and this model was used to estimate the annual excess number of deaths and hospitalizations attributable to influenza circulation among patients with heart failure in Denmark. The model also included data on weekly mean temperature and restricted cubic spline terms to account for seasonality and trends over time. RESULTS: Data were available from 2010 to 2018 encompassing 8 influenza seasons with an annual mean of 25,180 samples tested for influenza at Danish hospitals. Among an annual mean of 70,570 patients with heart failure, our model estimated that influenza activity was associated with an annual excess of 250 all-cause deaths (95% CI: 144-489 deaths) corresponding to 2.6% of all all-cause deaths (95% CI: 1.5%-5.1%) in patients with heart failure. Similarly, influenza activity was associated with an annual excess of 115 cardiovascular deaths (95% CI: 62-244 deaths) corresponding to 2.9% of all cardiovascular deaths (95% CI: 1.5%-6.1%). Influenza activity was also associated with an annual excess of 251 hospitalizations for pneumonia or influenza (95% CI: 107-533 hospitalizations) corresponding to 5.0% of all hospitalizations for pneumonia or influenza. CONCLUSIONS: Our results indicate that influenza activity likely causes substantial morbidity and mortality among patients with heart failure. Notably, our study suggests that approximately 2.6% of all deaths and 5.0% of all hospitalizations with influenza or pneumonia may be attributed to influenza in patients with heart failure.

Time of day for vaccination, outcomes, and relative effectiveness of high-dose vs. standard-dose quadrivalent influenza vaccine: A post hoc analysis of the DANFLU-1 randomized clinical trial.

OBJECTIVES: Morning influenza vaccination enhances antibody response. In this post hoc analysis of the DANFLU-1 trial, we sought to evaluate the association between time of day for vaccination (ToV) and outcomes and whether ToV modified the relative effectiveness of high-dose (QIV-HD) vs. standard-dose (QIV-SD) quadrivalent influenza vaccine. METHODS: DANFLU-1 was a pragmatic feasibility trial of QIV-HD vs. QIV-SD. Outcomes included hospitalizations and mortality. For subgroup analysis, the population was dichotomized at median ToV into two groups (early and late). RESULTS: The study population included 12,477 participants. Mean age was 71.7 ± 3.9 years with 5877 (47.1%) female participants. Median ToV was 11.29 AM. Earlier ToV was associated with fewer respiratory hospitalizations independent of vaccine type, which persisted in adjusted analysis (IRR 0.88 per 1-hour decrement (95% CI 0.78- 0.98, p = 0.025). No effect modification by continuous or dichotomous ToV was found. In subgroup analysis, effects consistently favored QIV-HD against hospitalizations for pneumonia or influenza (early: IRR 0.30; late: 0.29), all-cause hospitalizations (early: IRR 0.87; late: 0.86), and mortality (early: HR 0.53; late: 0.50). CONCLUSION: In this exploratory post hoc analysis, earlier ToV was associated with fewer respiratory hospitalizations. The relative effectiveness of QIV-HD vs. QIV-SD was not modified by ToV. Further research is needed to confirm findings. TRIAL REGISTRATION: Clinicaltrials.gov: NCT05048589.

Effect of low climate impact vs. high climate impact inhalers for patients with asthma and COPD-a nationwide cohort analysis.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) and asthma can be treated with inhaled corticosteroids (ICS) delivered by low climate impact inhalers (dry powder inhalers) or high climate impact inhalers (pressurized metered-dose inhalers containing potent greenhouse gasses). ICS delivered with greenhouse gasses is prescribed ubiquitously and frequent despite limited evidence of superior effect. Our aim was to examine the beneficial and harmful events of ICS delivered by low and high climate impact inhalers in patients with asthma and COPD. METHODS: Nationwide retrospective cohort study of Danish outpatients with asthma and COPD treated with ICS delivered by low and high climate impact inhalers. Patients were propensity score matched by the following variables; age, gender, tobacco exposure, exacerbations, dyspnoea, body mass index, pulmonary function, ICS dose and entry year. The primary outcome was a composite of hospitalisation with exacerbations and all-cause mortality analysed by Cox proportional hazards regression. RESULTS: Of the 10,947 patients with asthma and COPD who collected ICS by low or high climate impact inhalers, 2,535 + 2,535 patients were propensity score matched to form the population for the primary analysis. We found no association between high climate impact inhalers and risk of exacerbations requiring hospitalization and all-cause mortality (HR 1.02, CI 0.92-1.12, p = 0.77), nor on pneumonia, exacerbations requiring hospitalization, all-cause mortality, or all-cause admissions. Delivery with high climate impact inhalers was associated with a slightly increased risk of exacerbations not requiring hospitalization (HR 1.10, CI 1.01-1.21, p = 0.03). Even with low lung function there was no sign of a superior effect of high climate impact inhalers. CONCLUSION: Low climate impact inhalers were not inferior to high climate impact inhalers for any risk analysed in patients with asthma and COPD.

Electronic nudges for sustained influenza vaccination uptake in older adults: the nationwide randomized NUDGE-FLU-2 trial.

Digital letter interventions have proven effective in increasing influenza vaccination rates. In this trial, we sought to further refine these strategies and investigated whether the effectiveness of the strategies could be sustained across consecutive influenza seasons. We enrolled all eligible Danish citizens 65 years of age or older in a nationwide registry-based randomized implementation trial during the 2023-2024 influenza season. Households of participants were randomly assigned in a 2.45:1:1:1:1:1:1 ratio to usual care or six different behaviorally informed electronic letter-based nudges delivered before the influenza vaccination period. The primary endpoint was receipt of influenza vaccination. Statistical analyses accounted for household-level clustering. A total of 881,373 participants (mean age 74.1 ± 6.5 years, 52.1% female) were randomized across 649,487 households. The primary endpoint was met; influenza vaccination rates were higher in the pooled intervention letter group compared to usual care (76.32% versus 76.02%; difference, 0.31 percentage points; 99.29% confidence interval, 0.00-0.61; P = 0.007). Although no individual letter significantly increased influenza vaccination rates, the directionality of effect was consistent across all letters. Effectiveness was particularly pronounced in participants who had not received influenza vaccination during the preceding season (Pinteraction = 0.010). Effectiveness was consistent regardless of whether participants had received a similar electronic letter-based nudge in the preceding season (Pinteraction = 0.26). In summary, electronic letter-based nudges successfully increased influenza vaccination among older adults, and our results suggest that these highly scalable strategies can be implemented effectively and safely across consecutive vaccination seasons.ClinicalTrials.gov registration: NCT06030726 .

Adherence to glucagon-like peptide-1 receptor agonist treatment in type 2 diabetes mellitus: A nationwide registry study.

AIMS: To assess the level of adherence to glucagon-like peptide-1 receptor agonist (GLP-1RA) treatment using real-world data and to investigate the sociodemographic and clinical factors associated with discontinuation of GLP-1RAs. METHODS: First-time users of GLP-1RAs with type 2 diabetes mellitus (T2DM), aged ≥18 years, in the period 2007 to 2020, were identified using Danish registries, allowing all participants a minimum of 18 months' follow-up. Adherence to GLP-1RA therapy (medication possession ratio >0.80) and discontinuation of GLP-1RA therapy was estimated at 6- and 12-month follow-ups. Multivariable cause-specific Cox regression was used to identify sociodemographic and clinical factors associated with risk of discontinuation. RESULTS: In total, 44 343 first-time users of GLP-1RAs with T2DM were identified (mean age 58.6 years, 42.7% female, median duration of T2DM 6.8 years, median glycated haemoglobin level 65 mmol/mol). The absolute risk of discontinuing GLP-1RA treatment within 6 months was 14.2% (95% confidence interval [CI] 13.9-14.6) and 21.2% (95% CI 20.8-21.5) within 12 months. At 6 months, 50.4% were adherent to GLP-1RA therapy and at 12 months, 48.6% remained adherent. In the multivariable model, younger (<40 years) and older age (>75 years), higher Charlson Comorbidity Index score, lower household income, high school and longer university degree as educational attainment level, and longer diabetes duration were associated with a higher risk of discontinuing GLP-1RA treatment. CONCLUSION: Approximately one in five patients discontinued GLP-1RA therapy within the first 12 months and only half were adherent. Overall, lower socioeconomic status and higher comorbidity burden were associated with higher risk of discontinuing GLP-1RA treatment.

Prognostic importance of ischemic heart disease for patients with atrial fibrillation undergoing catheter ablation.

BACKGROUND: Ischemic heart disease (IHD) has been linked to an increased risk of atrial fibrillation (AF). However, data are sparse regarding the role of IHD in AF recurrence after catheter ablation. OBJECTIVE: We sought to investigate whether preexisting or new-onset IHD is associated with a greater risk of AF recurrence after ablation. METHODS: With use of Danish nationwide registries, all patients undergoing first-time AF ablation in Denmark from 2010 to 2020 were identified. The primary outcome was AF recurrence defined by AF-related hospital admission or antiarrhythmic drug use within 1 year after ablation excluding a 3-month blanking period. IHD was defined as an International Classification of Diseases, Tenth Revision diagnosis of IHD or prior coronary revascularization. RESULTS: Of 12,162 patients undergoing first-time ablation for AF (mean age, 62 years; 30% female), 20% had preexisting IHD. Preexisting IHD was associated with an increased risk of AF recurrence in univariable log-binomial logistic regression (relative risk, 1.09; 95% CI, 1.04-1.14; P < .001). However, after multivariable adjustment including procedural year, preexisting IHD was no longer associated with an increased risk of AF recurrence (relative risk, 1.02; 95% CI, 0.97-1.06; P = .42). In a nested case-control study of those without preexisting IHD before ablation (n = 9778), newly diagnosed IHD after ablation was associated with an increased risk of AF recurrence in multivariable analysis (hazard ratio, 3.03; 95% CI, 1.84-4.99; P < .001). CONCLUSION: The presence of IHD does not appear to reduce the effectiveness of AF ablation procedures. However, the emergence of IHD after AF ablation may serve as a trigger for AF that is insufficiently suppressed by prior ablation.

AM/PM dosing of LAMA for COPD: a randomized controlled trial protocol using digital recruitment and registries.

Rationale: Long-acting muscarinic antagonists (LAMAs) reduce the risk of acute exacerbations of chronic obstructive pulmonary disease (AECOPD), usually taken once daily in the morning. However, the circadian activity of autonomic regulation suggests that the highest need for anticholinergic therapy may be in the late night/early morning. This is supported by evidence that AECOPD most often begins in the morning. Furthermore, the trough spirometry effect of LAMA is lower than the peak effect, which further argues that evening dosing may be more optimal than morning dosing. This trial aims to determine whether evening administration of LAMA reduces hospitalization-requiring AECOPD or death from all causes within 1 year as compared to morning administration of the same LAMA. Methods: Randomized controlled open-label trial. Persons aged 30 years or older with a once-daily LAMA prescription and a confirmed COPD diagnosis were recruited. Participants were randomized in a 1:1 ratio to either morning or evening LAMA administration. Complete follow-up for the primary outcome, hospitalization-requiring AECOPD, or death from all causes within 1 year was captured from the Danish National Health Register, as were patient-reported outcome assessments at 6 and 12 months. Results: A total of 10,013 participants were randomized, and the recruitment process started on 9 March 2023. Secondary outcomes include (i) moderate COPD exacerbations; (ii) all-cause hospitalization; (iii) ICU admission; (iv) need for non-invasive ventilation; and (v) all-cause mortality, among others. All outcomes will be evaluated 12 months after recruitment.Clinical trial registration:ClinicalTrials.gov, NCT05563675.

Recurrent venous thromboembolism and vaginal estradiol in women with prior venous thromboembolism: A nested case-control study.

OBJECTIVES: Whether vaginal estradiol use is associated with an increased risk of recurrent venous thromboembolism (VTE) in women with prior VTE is unknown. We sought to evaluate the association between vaginal estradiol use and recurrent VTE in women with prior VTE. METHODS: We performed a nationwide nested case-control study among 44 024 women aged ≥45 years who developed a first VTE without a history of vaginal estrogen use prior to VTE diagnosis. Cases with recurrent VTE were matched 1:2 on birth year with controls using incidence density sampling. Exposure to vaginal estradiol tablets was categorized into current use (0-2 months before index), prior use (2-24 months before index) and past use (more than 24 months prior to index). RESULTS: We identified 5066 cases and 10 127 age-matched controls. In fully adjusted analysis vaginal estrogen was not associated with recurrent VTE with a hazard ratio of 0.75, p = .07 for current use, 0.83, p = .13 for prior use, and 1.24, p = .06 for past use. CONCLUSION: Use of vaginal estradiol tablets in women with prior VTE was not associated with an increased rate of recurrent VTE. Our study indicates that vaginal estradiol therapy is unlikely to increase risk of recurrent VTE in women with prior VTE.

Relative Effectiveness of High-Dose vs. Standard-Dose Quadrivalent Influenza Vaccine in Older Adults with Cardiovascular Disease: A Prespecified Analysis of the DANFLU-1 Randomized Clinical Trial.

Background: Influenza vaccination reduces the risk of adverse outcomes in patients with cardiovascular disease (CVD). We sought to evaluate whether the presence of CVD modified the relative effectiveness of high-dose (QIV-HD) vs. standard-dose (QIV-SD) quadrivalent influenza vaccine in this prespecified analysis of the DANFLU-1 trial. Methods: DANFLU-1 was a pragmatic, open-label, randomized feasibility trial of QIV-HD vs. QIV-SD in adults aged 65-79 years during the 2021/2022 influenza season in Denmark. Vaccines were allocated in a 1:1 ratio. Baseline and follow-up data regarding diagnoses and mortality were obtained from Danish national registers. The trial is registered at Clinicaltrials.gov: NCT05048589. The CVDs assessed included heart failure (HF), ischemic heart disease (IHD), atrial fibrillation, and a combined group denoted "chronic CVD" consisting of the aforementioned diseases, among others. Prespecified outcomes included hospitalizations for pneumonia or influenza, respiratory disease, CVD, cardiorespiratory disease, all-cause hospitalizations, and mortality. Effect modification was tested using interaction terms. Results: The final study population included 12,477 participants (mean age 71.7±3.9 years, 5,877 (47.1%) female), of whom 2,540 (20.4%) had chronic CVD. QIV-HD vs. QIV-SD was associated with a lower incidence of hospitalizations for pneumonia or influenza (IRR 0.30 (95%-CI 0.14-0.64)) and all-cause mortality (IRR 0.51 (0.30-0.86)) regardless of chronic CVD (p for interaction=0.57 and 0.49, respectively). The relative effectiveness of QIV-HD vs. QIV-SD against all-cause hospitalizations was modified in participants with chronic CVD (Overall: IRR 0.87 (0.76-0.99); no chronic CVD: 0.79 (0.67-0.92); chronic CVD: 1.11 (0.88-1.39); p for interaction=0.026). No other effect modification was observed by the presence of chronic CVD, HF, IHD, or atrial fibrillation. Conclusions: The relative effectiveness of QIV-HD vs. QIV-SD was consistent against hospitalizations for pneumonia or influenza and all-cause mortality regardless of chronic CVD. However, the relative effectiveness against all-cause hospitalizations was modified by the presence of chronic CVD. These results should be considered hypothesis-generating.

The relative vaccine effectiveness of high-dose vs standard-dose influenza vaccines in preventing hospitalization and mortality: A meta-analysis of evidence from randomized trials.

OBJECTIVES: To summarize current evidence of high-dose influenza vaccine (HD-IV) vs standard-dose (SD-IV) regarding severe clinical outcomes. METHODS: A prespecified meta-analysis was conducted to assess relative vaccine effectiveness (rVE) of HD-IV vs SD-IV in reducing the rates of (1) pneumonia and influenza (P&I) hospitalization, (2) all hospitalizations, and (3) all-cause death in adults ≥ 65 years in randomized controlled trials. Pooled effect sizes were estimated using fixed-effects models with the inverse variance method. RESULTS: Five randomized trials were included encompassing 105,685 individuals. HD-IV vs SD-IV reduced P&I hospitalizations (rVE: 23.5 %, [95 %CI: 12.3 to 33.2]). HD-IV vs SD-IV also reduced rate of all-cause hospitalizations (rVE: 7.3 %, [95 %CI: 4.5 to 10.0]). No significant differences were observed in death rates (rVE = 1.6 % ([95 %CI: -2.0 to 5.0]) in HD-IV vs SD-IV. Sensitivity analyses omitting trials with participants sharing the same comorbidity, trials with ≥ 100 events, and random-effects models provided comparable estimates for all outcomes. CONCLUSIONS: HD-IV reduced the incidence of P&I and all-cause hospitalization vs SD-IV in adults ≥ 65 years in randomized trials, through no significant difference was observed in all-cause death rates. These findings, supported by evidence from several randomized studies, can benefit from replication in a fully powered, individually randomized trial.

Effects of high-dose versus standard-dose quadrivalent influenza vaccine among patients with diabetes: A post-hoc analysis of the DANFLU-1 trial.

AIM: High-dose quadrivalent influenza vaccine (QIV-HD) has been shown to be more effective than standard-dose (QIV-SD) in reducing influenza infection, but whether diabetes status affects relative vaccine effectiveness (rVE) is unknown. We aimed to assess rVE on change in glycated haemoglobin [HbA1c (∆HbA1c)], incident diabetes, total all-cause hospitalizations (first + recurrent), and a composite of all-cause mortality and hospitalization for pneumonia or influenza. METHODS: DANFLU-1 was a pragmatic, open-label trial randomizing adults (65-79 years) 1:1 to QIV-HD or QIV-SD during the 2021/22 influenza season. Cox proportional hazards regression was used to estimate rVE against incident diabetes and the composite endpoint, negative binomial regression to estimate rVE against all-cause hospitalizations, and ANCOVA when assessing rVE against ∆HbA1c. RESULTS: Of the 12 477 participants, 1162 (9.3%) had diabetes at baseline. QIV-HD, compared with QIV-SD, was associated with a reduction in the rate of all-cause hospitalizations irrespective of diabetes [overall: 647 vs. 742 events, incidence rate ratio (IRR): 0.87, 95% CI (0.76-0.99); diabetes: 93 vs. 118 events, IRR: 0.80, 95% CI (0.55-1.15); without diabetes: 554 vs. 624 events, IRR: 0.88, 95% CI (0.76-1.01), pinteraction = 0.62]. Among those with diabetes, QIV-HD was associated with a lower risk of the composite outcome [2 vs. 11 events, HR: 0.18, 95% CI (0.04-0.83)] but had no effect on ∆HbA1c; QIV-HD adjusted mean difference: ∆ + 0.2 mmol/mol, 95% CI (-0.9 to 1.2). QIV-HD did not affect the risk of incident diabetes [HR 1.18, 95% CI (0.94-1.47)]. CONCLUSIONS: In this post-hoc analysis, QIV-HD versus QIV-SD was associated with an increased rVE against the composite of all-cause death and hospitalization for pneumonia/influenza, and the all-cause hospitalization rate irrespective of diabetes status.

Rationale and design of NUDGE-FLU-CHRONIC and NUDGE-FLU-2: Two nationwide randomized trials of electronic nudges to increase influenza vaccination among patients with chronic diseases and older adults during the 2023/2024 influenza season.

BACKGROUND: Yearly influenza vaccination is strongly recommended for older adults and patients with chronic diseases including cardiovascular disease (CVD); however, vaccination rates remain suboptimal, particularly among younger patients. Electronic letters incorporating behavioral nudges are highly scalable public health interventions which can potentially increase vaccination, but further research is needed to determine the most effective strategies and to assess effectiveness across different populations. The purpose of NUDGE-FLU-CHRONIC and NUDGE-FLU-2 are to evaluate the effectiveness of electronic nudges delivered via the Danish governmental electronic letter system in increasing influenza vaccination among patients with chronic diseases and older adults, respectively. METHODS: Both trials are designed as pragmatic randomized implementation trials enrolling all Danish citizens in their respective target groups and conducted during the 2023/2024 influenza season. NUDGE-FLU-CHRONIC enrolls patients aged 18-64 years with chronic diseases. NUDGE-FLU-2 builds upon the NUDGE-FLU trial conducted in 2022/2023 and aims to expand the evidence by testing both previously successful and new nudges among adults ≥65 years during a subsequent influenza season. Persons with exemptions from the electronic letter system are excluded from both trials. In both trials, participants are randomized in a 2.45:1:1:1:1:1:1 ratio to either receive no electronic letter (usual care) or to receive one of 6 different behaviorally informed electronic letters. NUDGE-FLU-CHRONIC has randomized 299,881 participants with intervention letters delivered on September 24, 2023, while NUDGE-FLU-2 has randomized 881,373 participants and delivered intervention letters on September 13, 2023. Follow-up is currently ongoing. In both trials, the primary endpoint is receipt of influenza vaccination on or before January 1, 2024, and the secondary endpoint is time to vaccination. Clinical outcomes including respiratory and cardiovascular hospitalizations, all-cause hospitalization, and mortality are included as prespecified exploratory endpoints. Prespecified individual-level pooled analyses will be conducted across NUDGE-FLU, NUDGE-FLU-CHRONIC, and NUDGE-FLU-2. DISCUSSION: NUDGE-FLU-CHRONIC is the first nationwide randomized trial of electronic nudges to increase influenza vaccination conducted among 18-64-year-old high-risk patients with chronic diseases. NUDGE-FLU-2 will provide further evidence on the effectiveness of electronic nudges among older adults ≥65 years. Collectively, the NUDGE-FLU trials will provide an extensive evidence base for future public health communications. TRIAL REGISTRATION: NUDGE-FLU-CHRONIC: Clinicaltrials.gov: NCT06030739, registered September 11, 2023, https://clinicaltrials.gov/study/NCT06030739. NUDGE-FLU-2: Clinicaltrials.gov: NCT06030726, registered September 11, 2023, https://clinicaltrials.gov/study/NCT06030726.

Clinical Outcomes With Electronic Nudges to Increase Influenza Vaccination : A Prespecified Analysis of a Nationwide, Pragmatic, Registry-Based, Randomized Implementation Trial.

BACKGROUND: In the NUDGE-FLU (Nationwide Utilization of Danish Government Electronic letter system for increasing inFLUenza vaccine uptake) trial, electronic letters incorporating cardiovascular (CV) gain-framing and repeated messaging increased influenza vaccination by approximately 1 percentage point. OBJECTIVE: To evaluate the effects of the successful nudging interventions on downstream clinical outcomes. DESIGN: Prespecified exploratory analysis of a nationwide randomized implementation trial. (ClinicalTrials.gov: NCT05542004). SETTING: The 2022 to 2023 influenza season. PARTICIPANTS: 964 870 Danish citizens aged 65 years or older. INTERVENTION: Usual care or 9 different electronically delivered behavioral nudging letters. MEASUREMENTS: Cardiovascular, respiratory, and other clinical end points during follow-up from intervention delivery (16 September 2022) through 31 May 2023. RESULTS: The analysis set included 691 820 participants. Hospitalization for pneumonia or influenza occurred in 3354 of 346 327 (1.0%) participants in the usual care group, 396 of 38 586 (1.0%) in the CV gain-framing group (hazard ratio [HR], 1.06 [95% CI, 0.95 to 1.18]; versus usual care), and 403 of 38 231 (1.1%) in the repeated letter group (HR, 1.09 [CI, 0.98 to 1.21]; versus usual care). In the usual care group, 44 682 (12.9%) participants were hospitalized for any cause, compared with 5002 (13.0%) in the CV gain-framing group (HR, 1.00 [CI, 0.97 to 1.03]; versus usual care) and 4965 (13.0%) in the repeated letter group (HR, 1.01 [CI, 0.98 to 1.04]; versus usual care). A total of 6341 (1.8%) participants died in the usual care group, compared with 721 (1.9%) in the CV gain-framing group (HR, 1.02 [CI, 0.94 to 1.10]; versus usual care) and 646 (1.7%) in the repeated letter group (HR, 0.92 [CI, 0.85 to 1.00]; versus usual care). LIMITATION: Prespecified but exploratory analysis, potential misclassification of events in routinely collected registry data, and results may not be generalizable to other health systems or countries with other racial compositions and/or cultural or societal norms. CONCLUSION: In a prespecified exploratory analysis, modest increases in influenza vaccination rates seen with electronic nudges did not translate into observable improvements in clinical outcomes. Seasonal influenza vaccination should remain strongly recommended. PRIMARY FUNDING SOURCE: Sanofi.

Effectiveness of high-dose versus standard-dose quadrivalent influenza vaccine against recurrent hospitalizations and mortality in relation to influenza circulation: A post-hoc analysis of the DANFLU-1 randomized clinical trial.

OBJECTIVES: To evaluate the relative effectiveness of high-dose quadrivalent influenza vaccine (QIV-HD) versus standard-dose quadrivalent influenza vaccine (QIV-SD) against recurrent hospitalizations and its potential variation in relation to influenza circulation. METHODS: We did a post-hoc analysis of a pragmatic, open-label, randomized trial of QIV-HD versus QIV-SD performed during the 2021-2022 influenza season among adults aged 65-79 years. Participants were enrolled in October 2021-November, 2021 and followed for outcomes from 14 days postvaccination until 31 May, 2022. We investigated the following outcomes: Hospitalizations for pneumonia or influenza, respiratory hospitalizations, cardio-respiratory hospitalizations, cardiovascular hospitalizations, all-cause hospitalizations, and all-cause death. Outcomes were analysed as recurrent events. Cumulative numbers of events were assessed weekly. Cumulative relative effectiveness estimates were calculated and descriptively compared with influenza circulation. The trial is registered at Clinicaltrials.gov: NCT05048589. RESULTS: Among 12,477 randomly assigned participants, receiving QIV-HD was associated with lower incidence rates of hospitalizations for pneumonia or influenza (10 vs. 33 events, incidence rate ratio [IRR] 0.30 [95% CI, 0.14-0.64]; p 0.002) and all-cause hospitalizations (647 vs. 742 events, IRR 0.87 [95% CI, 0.76-0.99]; p 0.032) compared with QIV-SD. Trends favouring QIV-HD were consistently observed over time including in the period before active influenza transmission; i.e. while the first week with a ≥10% influenza test positivity rate was calendar week 10, 2022, the first statistically significant reduction in hospitalizations for pneumonia or influenza was already observed by calendar week 3, 2022 (5 vs. 15 events, IRR 0.33 [95% CI, 0.11-0.94]; p 0.037). DISCUSSION: In a post-hoc analysis, QIV-HD was associated with lower incidence rates of hospitalizations for pneumonia or influenza and all-cause hospitalizations compared with QIV-SD, with trends evident independent of influenza circulation levels. Our exploratory results correspond to a number needed to treat of 65 (95% CI 35-840) persons vaccinated with QIV-HD compared with QIV-SD to prevent one additional all-cause hospitalization per season. Further research is needed to confirm these hypothesis-generating findings.

Electronically Delivered Nudges to Increase Influenza Vaccination Uptake in Older Adults With Diabetes: A Secondary Analysis of the NUDGE-FLU Trial.

Importance: Influenza vaccination is associated with a reduced risk of mortality in patients with diabetes, but vaccination rates remain suboptimal. Objective: To assess the effect of electronic nudges on influenza vaccination uptake according to diabetes status. Design, Setting, and Participants: The NUDGE-FLU (Nationwide Utilization of Danish Government Electronic Letter System for Increasing Influenza Vaccine Uptake) trial was a nationwide clinical trial of Danish citizens 65 years or older that randomized participants at the household level to usual care or 9 different electronic nudge letters during the 2022 to 2023 influenza season. End of follow-up was January 1, 2023. This secondary analysis of the NUDGE-FLU trial was performed from May to July 2023. Intervention: Nine different electronic nudge letters designed to boost influenza vaccination were sent in September to October 2022. Effect modification by diabetes status was assessed in a pooled analysis of all intervention arms vs usual care and for individual letters. Main Outcomes and Measures: The primary end point was receipt of a seasonal influenza vaccine. Results: The trial included 964 870 participants (51.5% female; mean [SD] age, 73.8 [6.3] years); 123 974 had diabetes. During follow-up, 83.5% with diabetes vs 80.2% without diabetes received a vaccine (P < .001). In the pooled analysis, nudges improved vaccination uptake in participants without diabetes (80.4% vs 80.0%; difference, 0.37 percentage points; 99.55% CI, 0.08 to 0.66), whereas there was no evidence of effect in those with diabetes (83.4% vs 83.6%; difference, -0.19 percentage points; 99.55% CI, -0.89 to 0.51) (P = .02 for interaction). In the main results of NUDGE-FLU, 2 of the 9 behaviorally designed letters (cardiovascular benefits letter and a repeated letter) significantly increased uptake of influenza vaccination vs usual care; these benefits similarly appeared attenuated in participants with diabetes (cardiovascular gain letter: 83.7% vs 83.6%; difference, 0.04 percentage points; 99.55% CI, -1.52 to 1.60; repeated letter: 83.5% vs 83.6%; difference, -0.15 percentage points; 99.55% CI, -1.71 to 1.41) vs those without diabetes (cardiovascular gain letter: 81.1% vs 80.0%; difference, 1.06 percentage points; 99.55% CI, 0.42 to 1.70; repeated letter: 80.9% vs 80.0%; difference, 0.87 percentage points; 99.55% CI, 0.22 to 1.52) (P = .07 for interaction). Conclusions and Relevance: In this exploratory subgroup analysis, electronic nudges improved influenza vaccination uptake in persons without diabetes, whereas there was no evidence of an effect in persons with diabetes. Trials are needed to investigate the effect of digital nudges specifically tailored to individuals with diabetes. Trial Registration: ClinicalTrials.gov Identifier: NCT05542004.