Immunogenicity of inactivated 2009 H1N1 influenza vaccine in pediatric liver transplant recipients.

To assess the safety and immunogenicity of 2009 H1N1 influenza vaccination, 13 pediatric liver transplant recipients and 31 immunocompetent controls received inactivated influenza vaccine without adjuvant according to Japanese guidelines. Serious adverse events and acute allograft rejections were not observed in participants. Seroprotection rates (hemagglutinin-inhibition (HI) antibody titer ≥ 1:40) were 53.8% among recipients and 58.1% among controls (p=0.797). Seroconversion rates (4-fold or more HI antibody rise) were 46.2% for the recipient group and 51.6% for the control group (p=0.741). Geometric mean titers were elevated after vaccination in both groups. In comparison with the seasonal influenza vaccination, the seroconversion rate for 2009 H1N1 appeared to be higher than that for seasonal influenza antigens, and the seroprotection rate for 2009 H1N1 clearly increased after vaccination. These findings suggest that pediatric liver transplant patients may respond safely to inactivated 2009 H1N1 influenza vaccines in a manner similar to immunocompetent children.