Infections represent a significant threat in solid-organ recipients. However, a certain number of infections can be prevented by immunizing patients before their transplantation. The aim of this study is to determine the level of immunity of children undergoing liver transplantation and to assess their capacity to maintain protective levels after surgery. Charts of 44 children transplanted with deceased donation livers between 1990 and 2002 at the Children's Hospital of Geneva were reviewed. Vaccine antibody responses were established pre- and post-transplantation. Only 43% of patients were up to date for diphtheria, tetanus, acellular pertussis, and polio vaccines at the pretransplantation visit, while 44% of children older than 12 months had received their required measles-mumps-rubella vaccines. Six of 44 children had received at least one dose of hepatitis B vaccine, while only two patients had received at least one dose of hepatitis A vaccine. After immunization, and one yr after transplantation, only 14 of 44 patients had detectable anti-HBs antibodies and seven of 18 had anti-HAV antibodies. Varicella antibodies were undetectable in 15 of 19 patients immunized prior to transplantation. This study highlights the need to enforce vaccination before transplantation, follow-up on vaccine- induced immunity, and adapt vaccination schedules after liver transplantation in children, especially for non-live vaccines, which are universally recommended in this population.