Effectiveness of high-dose vs. standard-dose quadrivalent influenza vaccine against recurrent hospitalisations and mortality in relation to influenza circulation: a post-hoc analysis of the DANFLU-1 randomised clinical trial
Abstract
OBJECTIVES
To evaluate the relative effectiveness of high-dose quadrivalent influenza vaccine (QIV-HD) vs. standard-dose quadrivalent influenza vaccine (QIV-SD) against recurrent hospitalisations and its potential variation in relation to influenza circulation.
METHODS
We did a post-hoc analysis of a pragmatic, open-label, randomised trial of QIV-HD vs. QIV-SD conducted during the 2021-2022 influenza season among adults aged 65-79 years. Participants were enrolled in October-November, 2021 and followed for outcomes from 14 days post-vaccination until May 31, 2022. We investigated the following outcomes: Hospitalisations for pneumonia or influenza, respiratory hospitalisations, cardio-respiratory hospitalisations, cardiovascular hospitalisations, all-cause hospitalisations, and all-cause death. Outcomes were analysed as recurrent events. Cumulative numbers of events were assessed weekly. Cumulative relative effectiveness estimates were calculated and descriptively compared to influenza circulation. The trial is registered at Clinicaltrials.gov: NCT05048589.
RESULTS
Among 12,477 randomly assigned participants, receiving QIV-HD was associated with lower incidence rates of hospitalisations for pneumonia or influenza (10 vs. 33 events, IRR 0.30 [95% CI 0.14-0.64], p=0.002) and all-cause hospitalisations (647 vs. 742 events, IRR 0.87 [95% CI 0.76-0.99], p=0.032) compared with QIV-SD. Trends favouring QIV-HD were consistently observed over time including in the period prior to…
How strong is the evidence?
Evidence Hub reads this as a secondary / pooled analysis, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence. Reported size: 12,477 participants or records.
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