ArticlePilot and feasibility studies2022
Feasibility of randomizing Danish citizens aged 65-79 years to high-dose quadrivalent influenza vaccine vs. standard-dose quadrivalent influenza vaccine in a pragmatic registry-based setting: rationale and design of the DANFLU-1 Trial.
Article in Pilot and feasibility studies, 2022. The graph could read no effect estimate from its abstract, so it casts no vote on the map. It is linked to trial NCT05048589 (Feasibility of Randomizing Danish Citizens Aged 65-79 Years to High-Dose Quadrivalent Influenza Vaccine vs. Standard-Dose Quadrivalent Influenza Vaccine in a Pragmatic Registry-Based Setting), which is not on this map. Cited by 12 papers, 2 of them syntheses that pooled it.
What it found
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Feasibility of Randomizing Danish Citizens Aged 65-79 Years to High-Dose Quadrivalent Influenza Vaccine vs. Standard-Dose Quadrivalent Influenza Vaccine in a Pragmatic Registry-Based Setting
Who cites it
12 citing papers in PubMed, 2 syntheses or guidelines pooled it.
- Protection against influenza hospitalizations from enhanced influenza vaccines among older adults: A systematic review and network meta-analysis.Journal of the American Geriatrics Society · 2024Pooled it
- Association of Influenza Vaccination With Cardiovascular Risk: A Meta-analysis.JAMA network open · 2022Pooled it
- Relative effectiveness of high-dose versus standard-dose influenza vaccine against hospitalizations and mortality according to Charlson Comorbidity Index: A post-hoc analysis of the DANFLU-1 randomized trial.European journal of clinical microbiology & infectious diseases : official publication of the European Society of Clinical Microbiology · 2026Trial
- Relative Effectiveness of High-Dose Versus Standard-Dose Influenza Vaccination Against Hospitalizations and Deaths According to Frailty Score: A Post Hoc Analysis of the DANFLU-1 Randomized Trial.The Journal of infectious diseases · 2026Trial
- High-Dose vs. Standard-Dose Influenza Vaccine in Older Patients With Hypertension: A Post Hoc Analysis of DANFLU-1.Journal of clinical hypertension (Greenwich, Conn.) · 2025Trial
- High-Dose Quadrivalent Influenza Vaccine for Prevention of Cardiovascular and Respiratory Hospitalizations in Older Adults.Influenza and other respiratory viruses · 2024Trial
- Clinical Trials With Pragmatic Elements: A Review of Use Cases and Real-World Data Utilization.Clinical pharmacology and therapeutics · 2025Review
- The silent exclusion: rethinking eligibility and generalizability in clinical trials.The Lancet regional health. Western Pacific · 2025Article
- Protecting the elderly from influenza in the context of immune system senescence. Elderly aged 65 and over are vulnerable to influenza and its associated complications.: Position paper by the Romanian Society of Gerontology and Geriatrics.Journal of medicine and life · 2024Article
- The Impact of Adjuvanted Influenza Vaccine on Disease Severity in the US: A Stochastic Model.Vaccines · 2023Article
- The impact of influenza vaccination on cardiovascular diseases.European heart journal supplements : journal of the European Society of Cardiology · 2023Article
- Vaccines in cardiology, an underutilized strategy to reduce the residual cardiovascular risk.Archivos peruanos de cardiologia y cirugia cardiovascularReview
Corrections and comments
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Authors and funding
17 authors.
Funding
Abstract
backgroundHigh-dose influenza vaccines provide better protection against influenza infection than standard-dose in persons aged 65 years and above; however, in most countries, high-dose vaccines are not widely implemented. Assessing the relative effectiveness of high-dose compared to standard-dose vaccines on hospitalizations and mortality would enable more robust public health and cost-effectiveness estimates. This study aims to investigate the feasibility of conducting a pragmatic randomized clinical trial in Denmark comparing high-dose to standard-dose vaccines utilizing existing vaccination infrastructure and the Danish nationwide health registries for data collection.
methodsThe DANFLU-1 trial (NCT05048589) is a pragmatic, open-label, active-controlled randomized trial randomizing Danish citizens aged 65-79 years to either high-dose quadrivalent influenza vaccine or standard-dose quadrivalent influenza vaccine. The study utilizes the infrastructure of a private vaccination provider (Danske Lægers Vaccinations Service) for recruitment, inclusion, randomization, and vaccination. All collection of baseline and follow-up data including safety monitoring is performed centrally by the Department of Cardiology at Herlev and Gentofte Hospital, Copenhagen, Denmark using the Danish nationwide health registries. The study aims to include 40,000 participants during the 2021/2022 influenza season. The primary endpoints address feasibility and include the number of participants enrolled, randomization balance, and representativeness compared to the Danish general population. Relative vaccine effectiveness will also be assessed, however, this feasibility study is not powered for clinical outcomes and may be affected by the COVID-19 pandemic. DISCUSSION: The DANFLU-1 study is investigating the feasibility of conducting a large-scale pragmatic clinical trial in Denmark utilizing existing infrastructure and the Danish nationwide registries. This will provide valuable insight, especially for potential future fully powered vaccine trials, but also for trials wishing to investigate other interventions.
trial registrationClinicaltrials.gov : NCT05048589 , registered September 17, 2021.
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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.