Influenza vaccination in solid organ transplant recipients: A systematic review and network meta-analysis of randomized trials

Background: Annual influenza vaccination is recommended for solid organ transplant (SOT) recipients, with various strategies explored to enhance efficacy. Given the ongoing uncertainty about the benefits and potential risks of different strategies in influenza vaccination in SOT recipients, comparing the indirect comparisons of the available evidence is necessary. Methods: We searched MEDLINE, Embase, CENTRAL, and CINAHL from inception to March 2025 to identify randomized controlled trials that compared different influenza vaccinations in SOT recipients. We conducted a network meta-analysis and used the GRADE approach to assess the certainty of evidence, categorize interventions, and present the findings. The protocol for this systematic review was registered in PROSPERO (CRD42024537277). Results: A total of 13 articles met our eligibility criteria (with 2,298 participants) and assessed 10 vaccination strategies. The high-dose (60IMSD) influenza vaccine was superior to the standard influenza vaccination regarding the seroconversion rate for H1N1 (RR 2.27, 95% CI 1.52 to 3.39; high certainty) and H3N2 (RR 1.61, 95% CI 1.34 to 1.94; high certainty). All of the included vaccination strategies might have no difference in graft rejection and other adverse events compared with the standard vaccination. Conclusion: We found that the 60IMSD vaccine demonstrated better immunogenicity outcomes compared with all other influenza vaccines studied in SOT recipients. Additionally, we observed little or no difference among various influenza vaccination strategies in terms of graft rejection and other serious adverse events (SAEs) or non–serious adverse events (non-SAEs).