Relative Effectiveness of High‐Dose vs. Standard‐Dose Influenza Vaccines in Preventing Hospitalizations: A National Retrospective Cohort Study in France, 2022/2023 Season

Background A French cohort study (2021/2022 influenza season) found the high‐dose influenza vaccine (HD) more effective than standard‐dose vaccines (SDs) in preventing influenza‐related hospitalizations in the elderly. The study continued to refine results and validate these findings. Methods Data from community‐dwelling 65+ adults who received HD or SD during the 2022/2023 vaccination campaign were extracted from the National Health database. Hospitalizations were recorded from 14 days postvaccination until June 30, 2023. HD and SD recipients were matched using a propensity score. Associations between vaccines and hospitalizations were assessed by estimating incidence rate ratios and converting them to HD vs. SD vaccine relative effectiveness (rVE). Results A total of 675,412 HD recipients were matched to 2,701,648 SD recipients. The rVE for influenza‐related hospitalizations was 27.4% [95% CI: 19.8; 34.3]. It ranged from 22.7% [9.8; 33.6] to 33.6% [21.2; 44.0] across age groups, indicating that HD consistently outperformed SDs in preventing influenza‐related hospitalizations, with the highest effect observed in 85+. Conclusions Our study is the first to publish rVE data comparing HD and SDs in a real‐world setting in France for the 2022/2023 influenza season. Its findings reaffirm the benefit of HD vs. SDs. HD could help reduce the burden of severe respiratory infections in the elderly.