Effectiveness and safety of inactivated influenza vaccination in pediatric liver transplant recipients over three influenza seasons.

Annual influenza vaccination is recommended for pediatric liver transplant recipients, who are at high risk of influenza-related complications. However, effectiveness and safety of vaccination may differ among influenza seasons in this population and have not been fully evaluated. Subjects comprised 38 pediatric liver transplant recipients with or without influenza vaccination through the 2006-2007, 2007-2008 and 2008-2009 influenza seasons. Recipients received inactivated trivalent (AH1/AH3/B) influenza vaccine, and comparisons were made to non-vaccinated recipients with regard to effectiveness and safety. No significant differences were seen between recipient groups for acute allograft rejection, acute febrile illness, or influenza virus infection. No serious systemic adverse events were observed in vaccinated recipients. Seroprotection rate (defined as the proportion of recipients with HI antibody titer ≥ 1:40), seroconversion rate (proportion of recipients with a ≥ 4-fold increase in HI titers), and geometric mean titers were mostly elevated after vaccination for the three influenza antigens in each season. These three indicators of immunogenicity showed similar results in both vaccinated recipients and vaccinated healthy children in the 2007-2008 season. These findings suggest that pediatric liver transplant patients may respond safely to inactivated seasonal influenza vaccines in a similar manner to healthy children, and effectiveness varies among influenza seasons.