Trial reportEuropean journal of clinical microbiology & infectious diseases : official publication of the European Society of Clinical Microbiology2026
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.
Trial report in European journal of clinical microbiology & infectious diseases : official publication of the European Society of Clinical Microbiology, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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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.
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Authors and funding
23 authors.
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Abstract
purposeThe DANFLU-1 trial suggested lower incidence of hospitalizations for pneumonia and influenza, respiratory disease and all-cause mortality among older adults receiving high-dose (HD-IV) versus standard-dose (SD-IV) influenza vaccine. This study assessed the relative effectiveness of HD-IV versus SD-IV according to comorbidity in elderly individuals.
methodsThis was a post-hoc analysis of the DANFLU-1 randomized controlled feasibility trial of HD-IV versus SD-IV conducted during the 2021-2022 influenza season in adults aged 65-79 years. Outcomes assessed included influenza-related, respiratory, and cardiovascular hospitalizations, and mortality. We tested for effect modification by level of the Charlson Comorbidity Index (CCI) using ICD-10 codes up to 10 years prior to randomization.
resultsOf the 12,477 randomly assigned participants (mean age 71.7 ± 3.9 years, 47.1% female), 8,020 (64.3%) had CCI = 0, 3,560 (28.5%) had CCI = 1-2 and 893 (7.2%) had CCI ≥ 3. When comparing HD-IV with SD-IV, hazard ratios of hospitalizations for pneumonia and influenza were similar across CCI groups (HR [95%CI]: 0.15 [0.03-0.68] for CCI = 0, 0.36 [0.11-1.15] for CCI = 1-2, 1.00 [0.25-4.00] for CCI ≥ 3). Comparable patterns were found for hospitalizations for respiratory disease (0.46 [0.17-1.20] for CCI = 0, 0.67 [0.32-1.39] for CCI = 1-2, 0.66 [0.24-1.87] for CCI ≥ 3) and all-cause mortality (0.28 [0.09-0.86] for CCI = 0, 0.70 [0.30-1.63] for CCI = 1-2, 0.57 [0.24-1.36] for CCI ≥ 3). There was no statistical evidence of effect modification by CCI for any outcome.
conclusionsThe lower incidences of clinical outcomes for HD-IV compared to SD-IV were not significantly modified by CCI. The potential benefit of HD-IV versus SD-IV may therefore be applicable regardless of comorbidity burden. Further research is required to confirm these findings.
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