Loading
Life sciences · Journal article
The Lancet. Healthy Longevity
No summary has been generated for this record yet. What follows is drawn from its source metadata only.
Journal article.
No findings were extractable from the material analysed.
Safety was not reported in the material analysed. Check the source before drawing any conclusion about harm.
The source did not state who this applies to in practice.
Graded across the dimensions that decide whether you should act, each from what the source actually supports. There is no single score, and where a dimension was not assessed it says so.
This record has not been graded across any dimension yet. Treat the label above as provisional and read the source.
What is missing. This record has no bottom line, key findings, reported figures, evidence dimensions. That is a gap in the analysis, not a judgement about the study.
Frailty is a major risk factor for influenza-related complications and can influence vaccine effectiveness. We aimed to assess the relative vaccine effectiveness (rVE) of high-dose (HD-IIV) versus standard-dose inactivated influenza vaccine (SD-IIV) in older adults aged 65 years or older according to frailty risk. This study was a prespecified analysis of DANFLU-2, an open-label, individually randomised trial, conducted in Denmark during three consecutive influenza seasons (2022-23, 2023-24, and 2024-25). Adults aged 65 years or older were randomised (1:1) to the HD-IIV or SD-IIV group. The primary endpoint was hospitalisation for influenza or pneumonia. Frailty was defined according to the validated Hospital Frailty Risk Score (HFRS) based on ICD-10 codes within 10 years before randomisation. Participants were stratified into three HFRS categories, namely low (<5 points), intermediate (5-15 points), and high (>15 points) frailty risk. The rVE of HD-IIV versus SD-IIV against the primary endpoint was assessed across prespecified HFRS categories and treating HFRS as a continuous variable. Pearson's chi-square test was used to compare safety events across frailty risk groups and randomisation groups. Among 332 438 randomised participants (mean age 73·7 years [SD 5·8]; 161 538 [48·6%] were female), 276 173 (83·1%) had low frailty risk, 52 395 (15·8%) had intermediate frailty risk, and 3861 (1·2%) had high frailty risk. The primary endpoint of hospitalisation for influenza or pneumonia occurred in 1424 (0·5%) of 276 173 participants with low frailty risk, 761 (1·5%) of 52 395 with intermediate frailty risk, and 163 (4·2%) of 3861 with high frailty risk (relative risk [RR] for intermediate vs low frailty risk 2·8 [95% CI 2·6-3·1]; RR for high vs low frailty risk 8·2 [7·0-9·6]). HFRS as a continuous variable significantly modified the effect of HD-IIV versus SD-IIV against the primary endpoint with higher rVE estimates with increasing HFRS (pinteraction=0·020). The rVE was 0·2% (95% CI -10·8 to 10·2) among those with low frailty risk, 13·1% (-0·4 to 24·8) among those with intermediate frailty risk, and 19·9% (-10·3 to 42·1) among those with high frailty risk. No significant interaction was observed when HFRS was assessed according to the prespecified categorical frailty groups (pinteraction=0·17). The proportion of participants with at least one serious adverse event increased across frailty risk groups (13 366 [4·8%] of 275 795 for low frailty risk, 5475 [10·5%] of 52 315 for intermediate frailty risk, and 777 [20·2%] of 3850 for high frailty risk; p<0·0001), with similar proportions of serious adverse events in the HD-IIV and SD-IIV groups for each frailty risk group. Among adults aged 65 years or older in Denmark, frailty risk might modify the effects of HD-IIV versus SD-IIV against hospitalisation for influenza or pneumonia, with higher rVE estimates with increasing frailty risk. These findings might support considering high-dose influenza vaccines for frail older adults. However, effect modification was not evident when frailty was assessed using prespecified categorical subgroups, and subgroup-specific estimates were imprecise, with 95% CIs crossing the null. These results should be considered exploratory, warranting further investigation. The DANFLU-2 trial was funded by Sanofi.