The relative vaccine effectiveness of high-dose vs standard-dose influenza vaccines in preventing hospitalization and mortality: A meta-analysis of evidence from randomized trials.

Skaarup KG, Lassen MCH, Modin D, Johansen ND, Loiacono MM, Harris RC, Lee JKH, Dufournet M, Vardeny O, Peikert A, Claggett B, Solomon SD, Jensen JUS, Biering-Sørensen T. The relative vaccine effectiveness of high-dose vs standard-dose influenza vaccines in preventing hospitalization and mortality: A meta-analysis of evidence from randomized trials. The Journal of Infection. 2024 Jul 1; 89(1):106187.

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Abstract:

OBJECTIVES: To summarize current evidence of high-dose influenza vaccine (HD-IV) vs standard-dose (SD-IV) regarding severe clinical outcomes. METHODS: A prespecified meta-analysis was conducted to assess relative vaccine effectiveness (rVE) of HD-IV vs SD-IV in reducing the rates of (1) pneumonia and influenza (PandI) hospitalization, (2) all hospitalizations, and (3) all-cause death in adults =  65 years in randomized controlled trials. Pooled effect sizes were estimated using fixed-effects models with the inverse variance method. RESULTS: Five randomized trials were included encompassing 105,685 individuals. HD-IV vs SD-IV reduced PandI hospitalizations (rVE: 23.5 %, [95 %CI: 12.3 to 33.2]). HD-IV vs SD-IV also reduced rate of all-cause hospitalizations (rVE: 7.3 %, [95 %CI: 4.5 to 10.0]). No significant differences were observed in death rates (rVE = 1.6 % ([95 %CI: -2.0 to 5.0]) in HD-IV vs SD-IV. Sensitivity analyses omitting trials with participants sharing the same comorbidity, trials with =  100 events, and random-effects models provided comparable estimates for all outcomes. CONCLUSIONS: HD-IV reduced the incidence of PandI and all-cause hospitalization vs SD-IV in adults =  65 years in randomized trials, through no significant difference was observed in all-cause death rates. These findings, supported by evidence from several randomized studies, can benefit from replication in a fully powered, individually randomized trial.