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| ID | Type | Description | Link |
|---|---|---|---|
| QHD00027 | Other Identifier | Sanofi Pasteur | |
| 2021-003170-31 | EudraCT Number |
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| Name | Class |
|---|---|
| Sanofi Pasteur, a Sanofi Company | INDUSTRY |
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The purpose of the study is to assess the feasibility of identifying, recruiting and randomizing a large sample of Danish citizens aged 65-79 years to high-dose quadrivalent influenza vaccine or standard-dose quadrivalent influenza vaccine in the 2021/2022 influenza season in a registry-based setting using Danish nationwide registries for all data collection including baseline information and outcome assessment.
To evaluate the feasibility of recruiting and randomizing Danish citizens aged 65-79 years, we aim to randomize 40,000 citizens 1:1 to high-dose quadrivalent influenza vaccine or standard-dose quadrivalent influenza vaccine in a pragmatic, open-label, registry-based design using the infrastructure of Danske Lægers Vaccinations Service (DLVS), an organization responsible for numerous vaccination clinics in Denmark, for recruitment and randomization and Danish nationwide registries for data collection. Citizens will be recruited by DLVS and randomized and vaccinated at the DLVS clinics. All collection of data related to baseline information, outcomes, and safety monitoring will be performed by a central trial site utilizing information from Danish nationwide health registries.
The findings of this pilot trial will indicate whether the conduction of a full-scale, adequately powered pragmatic RCT is feasible within the Danish registry-based framework.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Standard-Dose Quadrivalent Influenza Vaccine | Active Comparator | QIV-SD single injection at Day 0 |
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| High-Dose Quadrivalent Influenza Vaccine | Experimental | QIV-HD single injection at Day 0 |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Standard-Dose Quadrivalent Influenza Vaccine | Drug | For the control arm, the standard-dose quadrivalent influenza vaccines Influvactetra® and Vaxigriptetra will be used. |
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| Measure | Description | Time Frame |
|---|---|---|
| Number of persons contacted by recruitment letter | Up to 8 months | |
| Number of participants included and randomized to QIV-HD or QIV-SD | Up to 8 months | |
| Agreement between randomization assignment and actual received vaccine | Up to 8 months | |
| Balance between groups in terms of number of subjects in each arm and baseline characteristics | Up to 8 months | |
| Comparison of baseline characteristics for the QIV-HD and QIV-SD groups to the overall Danish general population aged 65-79 years | Up to 8 months | |
| Comparison of baseline characteristics for the QIV-HD and QIV-SD groups to the population aged 65-79 years in the DLVS database used for recruitment | Up to 8 months | |
| Description of event rates and calculation of relative vaccine effectiveness for hospitalization for influenza and/or pneumonia | First hospitalization with a primary (A) diagnosis code for influenza or pneumonia of at least 1 night duration | >= 14 days after vaccination up to 8 months post-vaccination |
| Description of event rates and calculation of relative vaccine effectiveness for hospitalization for respiratory disease | First hospitalization with a primary (A) diagnosis code for respiratory disease of at least 1 night duration | >= 14 days after vaccination up to 8 months post-vaccination |
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Inclusion Criteria:
Exclusion Criteria:
1. Allergy/hypersensitivity towards the influenza vaccines used in this study
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| Name | Affiliation | Role |
|---|---|---|
| Tor Biering-Sørensen, MD, PhD, MPH | Research Director | Study Chair |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Cardiovascular Non-Invasive Imaging Research Laboratory, Department of Cardiology, Herlev and Gentofte Hospital | Hellerup | 2900 | Denmark |
| PubMed Identifier | Type | Citation | Retractions |
|---|---|---|---|
| 41985620 | Derived | Christensen J, Johansen ND, Bernholm KF, Borchsenius JIH, Janstrup KH, Modin D, Skaarup KG, Nealon J, Samson S, Loiacono M, Huang Y, Harris R, Larsen CS, Jensen AMR, Landler NE, Claggett BL, Solomon SD, Gislason GH, Kober L, Landray MJ, Sivapalan P, Jensen JUS, Biering-Sorensen T. Positive predictive value of respiratory infection diagnoses in the Danish National Patient Registry: A post hoc validation analysis of the DANFLU-1 trial. Int J Infect Dis. 2026 Jul;168:108703. doi: 10.1016/j.ijid.2026.108703. Epub 2026 Apr 13. | |
| 41238377 |
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Sharing of individual-level data stemming from Danish administrative registries is illegal according to Danish law.
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| Type | Date | Date Unknown |
|---|---|---|
| Release | Nov 20, 2023 | |
| Reset | Apr 26, 2024 |
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| High-Dose Quadrivalent Influenza Vaccine | Drug | For the control arm, the high-dose quadrivalent influenza vaccine Efluelda®/Fluzone® High-Dose Quadrivalent will be used. |
|
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| Description of event rates and calculation of relative vaccine effectiveness for hospitalization for cardio-respiratory disease | First hospitalization with a primary (A) diagnosis code for cardio-respiratory disease of at least 1 night duration | >= 14 days after vaccination up to 8 months post-vaccination |
| Description of event rates and calculation of relative vaccine effectiveness for hospitalization for cardiovascular disease | First hospitalization with a primary (A) diagnosis code for cardiovascular disease of at least 1 night duration | >= 14 days after vaccination up to 8 months post-vaccination |
| Description of event rates and calculation of relative vaccine effectiveness for hospitalization from any cause | First hospitalization with any diagnosis code of at least 1 night duration | >= 14 days after vaccination up to 8 months post-vaccination |
| Description of event rates and calculation of relative vaccine effectiveness for all-cause mortality | Death from any cause | >= 14 days after vaccination up to 8 months post-vaccination |
| Description of event rates and calculation of relative vaccine effectiveness for hospitalization for COVID-19 | First hospitalization with a primary (A) diagnosis code for COVID-19 of at least 1 night duration | >= 14 days after vaccination up to 8 months post-vaccination |
| Danske Lægers Vaccinations Service | Søborg | 2860 | Denmark |
| Derived |
| Langhoff AF, Johansen ND, Modin D, Janstrup KH, Bartholdy KV, Espersen C, Nealon J, Samson S, Loiacono MM, Harris R, Larsen CS, Jensen AMR, Landler NE, Claggett BL, Solomon SD, Landray MJ, Gislason GH, Kober L, Sivapalan P, Jensen JUS, Biering-Sorensen T. High-Dose vs. Standard-Dose Influenza Vaccine in Older Patients With Hypertension: A Post Hoc Analysis of DANFLU-1. J Clin Hypertens (Greenwich). 2025 Nov;27(11):e70177. doi: 10.1111/jch.70177. |
| 41177098 | Derived | Duus LS, Johansen ND, Modin D, Janstrup KH, Nealon J, Samson S, Loiacono MM, Harris RC, Larsen CS, Reimer Jensen AM, Claggett BL, Solomon SD, Landray MJ, Gislason GH, Kober L, Sivapalan P, Staehr Jensen JU, Biering-Sorensen T. Effects of high-dose versus standard-dose influenza vaccine among patients with chronic lung disease: A prespecified analysis of the DANFLU-1 trial. Respir Investig. 2025 Nov;63(6):1309-1315. doi: 10.1016/j.resinv.2025.10.016. Epub 2025 Nov 1. |
| 39303788 | Derived | Christensen J, Johansen ND, Janstrup KH, Modin D, Skaarup KG, Nealon J, Samson S, Loiacono M, Harris R, Larsen CS, Jensen AMR, Landler NE, Claggett BL, Solomon SD, Gislason GH, Kober L, Landray MJ, Sivapalan P, Jensen JUS, Biering-Sorensen T. 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. J Infect. 2024 Nov;89(5):106276. doi: 10.1016/j.jinf.2024.106276. Epub 2024 Sep 18. |
| 39215646 | Derived | Christensen J, Johansen ND, Modin D, Janstrup KH, Nealon J, Samson S, Loiacono M, Harris R, Larsen CS, Jensen AMR, Landler NE, Claggett BL, Solomon SD, Gislason GH, Kober L, Landray MJ, Sivapalan P, Jensen JUS, Biering-Sorensen T. Relative Effectiveness of High-Dose Versus Standard-Dose Quadrivalent Influenza Vaccine in Older Adults With Cardiovascular Disease: A Prespecified Analysis of the DANFLU-1 Randomized Clinical Trial. Circ Cardiovasc Qual Outcomes. 2025 Feb;18(2):e011496. doi: 10.1161/CIRCOUTCOMES.124.011496. Epub 2024 Aug 31. |
| 38586966 | Derived | Lassen MCH, Johansen ND, Modin D, Nealon J, Samson S, Dufournet M, Loiacono MM, Larsen CS, Jensen AMR, Landler NE, Claggett BL, Solomon SD, Landray MJ, Gislason GH, Kober L, Jensen JUS, Sivapalan P, Vestergaard LS, Krause TG, Biering-Sorensen T. Effects of high-dose versus standard-dose quadrivalent influenza vaccine among patients with diabetes: A post-hoc analysis of the DANFLU-1 trial. Diabetes Obes Metab. 2024 May;26(5):1821-1829. doi: 10.1111/dom.15498. |
| 38320035 | Derived | Johansen ND, Modin D, Nealon J, Samson S, Salamand C, Loiacono MM, Larsen CS, Jensen AMR, Landler NE, Claggett BL, Solomon SD, Landray MJ, Gislason GH, Kober L, Jensen JUS, Sivapalan P, Vestergaard LS, Valentiner-Branth P, Krause TG, Biering-Sorensen T. A Pragmatic Randomized Feasibility Trial of Influenza Vaccines. NEJM Evid. 2023 Feb;2(2):EVIDoa2200206. doi: 10.1056/EVIDoa2200206. Epub 2023 Jan 23. |
| 38286177 | Derived | Johansen ND, Modin D, Skaarup KG, Nealon J, Samson S, Dufournet M, Loiacono MM, Harris RC, Larsen CS, Jensen AMR, Landler NE, Claggett BL, Solomon SD, Landray MJ, Gislason GH, Kober L, Jensen JUS, Sivapalan P, Vestergaard LS, Valentiner-Branth P, Krause TG, Biering-Sorensen T. 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. Clin Microbiol Infect. 2024 Nov;30(11):1453-1459. doi: 10.1016/j.cmi.2024.01.017. Epub 2024 Jan 28. |
| 35449028 | Derived | Johansen ND, Modin D, Nealon J, Samson S, Salamand C, Larsen CS, Claggett BL, Solomon SD, Landray MJ, Gislason GH, Kober L, Jensen JUS, Sivapalan P, Vestergaard LS, Valentiner-Branth P, Krause TG, Biering-Sorensen T. 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. Pilot Feasibility Stud. 2022 Apr 21;8(1):87. doi: 10.1186/s40814-022-01044-w. |
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| Release Date | Unrelease Date | Unrelease Date Unknown | Reset Date | MCP Release Number |
|---|---|---|---|---|
| Nov 20, 2023 | Apr 26, 2024 |
| ID | Term |
|---|---|
| D007251 | Influenza, Human |
| ID | Term |
|---|---|
| D012141 | Respiratory Tract Infections |
| D007239 | Infections |
| D009976 | Orthomyxoviridae Infections |
| D012327 | RNA Virus Infections |
| D014777 | Virus Diseases |
| D012140 | Respiratory Tract Diseases |
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| ID | Term |
|---|---|
| D007252 | Influenza Vaccines |
| ID | Term |
|---|---|
| D014765 | Viral Vaccines |
| D014612 | Vaccines |
| D001688 | Biological Products |
| D045424 | Complex Mixtures |
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