RESUMO
Background: Immunogenicity of influenza vaccine in transplant recipients is suboptimal and alternative vaccination regimens are necessary. Methods: We compared the immunogenicity of a standard-dose trivalent inactivated influenza vaccination (SDTIIV), double-dose trivalent inactivated influenza vaccination (DDTIIV) and booster-dose trivalent inactivated influenza vaccination (BDTIIV) of the 2014 seasonal trivalent inactivated influenza vaccine in kidney transplant recipients. We randomized 176 participants to SDTIIV (59), DDTIIV (59) and BDTIIV regimens (58). Antibody titres were determined by hemagglutination inhibition at enrollment and 21 days post-vaccination. Seroprotection rates (SPR), seroconversion rates (SCR) and geometric mean ratios (GMR) were analyzed separately for participants with low (<1:40) and high (≥1:40) pre-vaccination antibody titres. Results: Vaccination was confirmed for 172 participants. Immunogenicity analysis was done for 149 participants who provided post-vaccination blood samples. In the subgroup with high pre-vaccination antibody titres, all vaccination regimens induced SPR >70% to all antigens, but SCR and GMR were below the recommendations. In the subgroup with low pre-vaccination antibody titres, DDTIIV and BDTIIV regimens induced adequate SCR >40% and GMR >2,5 for all antigens, while SDTIIV achieved the same outcomes only for influenza B. SPR were >70% only after DDTIIV (A/H1N1 - 77.8%) and BDTIIV (A/H3N2 - 77.8%). BDTIIV regimen independently increased seroprotection to A/H1N1 (PR=2.58; p=0.021) and A/H3N2 (PR=2.21; p=0.004), while DDTIIV independently increased seroprotection to A/H1N1 (PR=2.59; p=0.021). Conclusion: Our results suggest that DDTIIV and BDTIIV regimens are more immunogenic than SDTIIV, indicating the need for head-to-head multicenter clinical trials to further evaluate their efficacy.