Safety and efficacy of high-dose versus standard-dose influenza vaccines in hematopoietic stem cell transplant recipients: A meta-analysis of randomized controlled trials

Abstract

Given the vulnerability of hematopoietic cell transplant (HCT) patients to influenza infection and its complications, annual vaccination is recommended. However, vaccination was known to be less effective in these patients. Multiple studies have assessed various effects in HCT recipients after receiving different vaccine doses. However, the results have been inconclusive. This meta-analysis aims to provide a comprehensive analysis of the effectiveness and safety of HCT recipients when they receive a higher and standard dose of influenza vaccines. This study used PRISMA guidelines on several databases until Oct 25, 2024. We used ROB 2.0 and Review Manager 5.4 Software for further analysis. We included four low-risk of bias studies, and we conducted further analysis. The efficacy of HAI titer $\ge$ 1:40, >4-fold, and confirmed influenza positives was comparable in both groups, with insignificant results in each follow-up group. However, the adverse effect was found significantly higher in the high-dose group, specifically the local adverse effect (p < 0.0001). High-dose influenza vaccines showed higher adverse events and more confirmed influenza cases than standard-dose, suggesting standard-dose may be preferable post-HCT. These findings underscore the need for further research, particularly in diverse populations and vulnerable groups.