Heart failure & cardiomyopathies
High-Dose Versus Standard-Dose Influenza Vaccine in Heart Failure: A Prespecified Analysis of the DANFLU-2 Trial
Authors' conclusion
In this prespecified exploratory analysis of the largest individually randomized influenza vaccine trial ever conducted, HD-IIV was associated with lower rates of influenza and cardiovascular hospitalizations compared with SD-IIV, with effect estimates similar across HF status at baseline and HF subgroups.
Study context
- Population
- Citizens ≥65 years in Denmark, 2022/2023 to 2024/2025 influenza seasons, by heart failure (HF) status10,410 with HF
- Participants
- 332,438 participants
- Comparison
- High-dose inactivated influenza vaccine (HD-IIV) vs standard-dose inactivated influenza vaccine (SD-IIV) by HF status
- Primary endpoint
- Hospitalization for influenza-related illness, laboratory-confirmed influenza, any CVD, cardio-respiratory disease and HF, by HF status
Methodological detailsprespecified exploratory analysis, individually randomized, open-label, registry-based end point evaluation, 1:1 randomization
- Prespecified exploratory analysis
- Individually randomized
- Open-label
- Registry-based end point evaluation
- 1:1 randomization
Primary result
As reported in the abstract
Hospitalization outcomes in participants with HF at baseline (HD-IIV vs SD-IIV, RR)
- Influenza-related hospitalization, RR
- 0.48 (95% CI 0.20-1.06; Pinteraction=0.64)
- Laboratory-confirmed influenza hospitalization, RR
- 0.55 (95% CI 0.29-1.02; Pinteraction=0.59)
- Cardio-respiratory hospitalization, RR
- 0.89 (95% CI 0.77-1.02; Pinteraction=0.34)
- CV hospitalization, RR
- 0.86 (95% CI 0.72-1.02; Pinteraction=0.34)
- HF hospitalization, RR
- 0.82 (95% CI 0.61-1.11; Pinteraction=0.83)
Further findings
All outcomes, overall population
- HD-IIV associated with significantly lower incidence of hospitalization for influenza-related illness, laboratory-confirmed influenza, cardio-respiratory disease, CVD and HF vs SD-IIV
HF subgroups (disease duration, recency of hospitalization, most recent NT-proBNP, device therapy)
- Findings consistent across HF subgroups
Original publication
High-Dose Versus Standard-Dose Influenza Vaccine in Heart Failure: A Prespecified Analysis of the DANFLU-2 Trial. Circ Heart Fail. Published 30 August 2025. doi:10.
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