Recent trial evidence supports enhanced influenza vaccines for older adults: implications for Belgian practice

OBJECTIVES: To synthesize evidence on enhanced influenza vaccine effectiveness in older adults and contextualize the 2026-2027 Belgian recommendations for clinical practice. METHODS: Narrative review of randomized trials, observational studies, and meta-analyses examining HD-IIV and A-IIV in adults aged ≥ 65 years, with emphasis on European data published between 2020 and 2026. RESULTS: = 466,320) demonstrated relative vaccine effectiveness (rVE) of 31.9% (95% CI 19.7-42.2) for HD-IIV versus SD-IIV against laboratory-confirmed influenza hospitalization. DANFLU-2 subgroup analyses identified chronic kidney disease (CKD) as a modifier of enhanced vaccine benefit (rVE 68.6% in CKD versus 30.6% in non-CKD). A-IIV demonstrates comparable benefits in observational studies, though randomized trial evidence remains less extensive. Both enhanced vaccines demonstrated clinical superiority over standard-dose vaccines. Randomized trial evidence supports HD-IIV whereas clinical effectiveness data for A-IIV rely primarily on observational studies. Both formulations show acceptable safety profiles. The Superior Health Council (SHC) recommends HD-IIV or A-IIV for adults aged ≥ 65 years. CONCLUSIONS: Randomized trial evidence supports HD-IIV whereas clinical effectiveness data for A-IIV rely primarily on observational studies. The SHC guidelines introduce age-stratified recommendation strength (conditional for 65-74 years; strong for ≥75 years) and extend consideration of enhanced vaccines to adults aged 50-64 years with CKD.