Assessing High-Dose Versus Standard-Dose Influenza Vaccine Protection Against Severe Outcomes in Older Adults with Chronic Conditions

Among older adults (≥65 years) hospitalized with influenza in the USA in 2025-26, 33.9% had renal disease and 44.2% had chronic lung disease.5 466,320 participants enrolled across Denmark and Spain 9 Prespecified pooled analysis of methodologically harmonized, individually randomized DANFLU-2 7 and GALFLU 8 trials 9 Why Chronic Conditions Matter HD-IIV FLUNITY-HD Study Design Hospitalization for Pneumonia or Influenza Benefit of HD-IIV vs SD-IIV Methodologically harmonized 332k participants DANFLU-2 HD-IIV vs SD-IIV against hospitalizations Denmark ≥65 years 134k participants NH23/24 -24/25 NH22/23, 23/24, and 24/25 GALFLU HD-IIV vs SD-IIV against hospitalizations Galicia, Spain 65-79 yearsThe largest individually randomized influenza vaccine effectiveness study in older adults.9 FLUNITY-HD (Pooled Analysis) 9 Flu seasons