Pooled Analysis of Methodologically Harmonized Pragmatic Randomized Trials of High-Dose vs. Standard-Dose Influenza Vaccine Against Severe Clinical Outcomes

Summary

This prespecified analysis will pool the datasets from two pragmatic randomized trials evaluating the relative vaccine effectiveness of high-dose vs. standard-dose influenza vaccine against severe clinical outcomes: the DANFLU-2 (A Pragmatic Randomized Trial to Evaluate the Effectiveness of High-Dose Quadrivalent Influenza Vaccine vs. Standard-Dose Quadrivalent Influenza Vaccine in Older Adults) trial and the GALFLU (Pragmatic Randomized Trial to Evaluate the Effectiveness of High-Dose Quadrivalent Influenza Vaccine vs. Standard-Dose Quadrivalent Influenza Vaccine in Adults Aged 65 to 79 Years in Galicia, Spain) trial. The purpose of the pooled analysis is to ensure adequate statistical power for evaluating relative vaccine effectiveness against severe clinical outcomes and to increase generalizability of the results by combining data from two countries.

Timeline

Start

2025-05-31

Primary completion

2025-05-31

Completion

2025-08-31

Publications

• Johansen ND, Modin D, Pardo-Seco J, Rodriguez-Tenreiro-Sanchez C, Loiacono MM, Harris RC, Dufournet M, van Aalst R, Chit A, Larsen CS, Larsen L, Wiese L, Dalager-Pedersen M, Claggett BL, Janstrup KH, Duran-Parrondo C, Pineiro-Sotelo M, Cribeiro-Gonzalez M, Conde-Pajaro M, Miras-Carballal S, Gonzalez-Perez JM, Solomon SD, Sivapalan P, Martel CJ, Jensen JUS, Martinon-Torres F, Biering-Sorensen T; DANFLU-2 Study Group and the GALFLU Trial Team. High-Dose Versus Standard-Dose Influenza Vaccine and Cardiovascular Outcomes in Older Adults: The FLUNITY-HD Prespecified Pooled Analysis. Circulation. 2026 Mar 17;153(11):798-806. doi: 10.1161/CIRCULATIONAHA.125.077801. Epub 2025 Nov 10.
• Johansen ND, Modin D, Pardo-Seco J, Rodriguez-Tenreiro-Sanchez C, Loiacono MM, Harris RC, Dufournet M, van Aalst R, Chit A, Larsen CS, Larsen L, Wiese L, Dalager-Pedersen M, Claggett BL, Janstrup KH, Duran-Parrondo C, Pineiro-Sotelo M, Cribeiro-Gonzalez M, Conde-Pajaro M, Miras-Carballal S, Gonzalez-Perez JM, Solomon SD, Sivapalan P, Martel CJ, Jensen JUS, Martinon-Torres F, Biering-Sorensen T; DANFLU-2 Study Group; GALFLU Trial Team. Effectiveness of high-dose influenza vaccine against hospitalisations in older adults (FLUNITY-HD): an individual-level pooled analysis. Lancet. 2025 Nov 22;406(10518):2425-2434. doi: 10.1016/S0140-6736(25)01742-8. Epub 2025 Oct 17.

Drugs

Indications