Immunogenicity of varicella zoster vaccine in pediatric liver transplantation.

Background Pediatric liver transplant (LT) candidates often miss complete VZV vaccination before LT. We aimed to evaluate the immunogenicity of two doses of VZV vaccines in pediatric LT candidates younger than 2 years and its persistence of immunogenicity after LT. Methods Patients aged 9-24 months were enrolled before LT. The first dose of VZV vaccine was given at 9 months, and the second dose was given at 1 to 3 months apart and at least 4 weeks before LT. Varicella-Zoster IgG (VZG) was used to detect immunoglobulin G antibodies to VZV and was reported as test value (TV). TV ≥ 0.9 was considered as seropositive. TV was measured at enrollment, 1 month after the first and the second dose, before LT, 3 and 6 months after LT. Results Fourteen children were enrolled in this prospective cohort study. The median age at the first and the second dose of VZV vaccine was 11.5 (IQR 9, 12) and 13 (IQR 12, 33) months, respectively. The seroconversion rate was 66.7% (8/12) and 70% (7/10) after one and two VZV vaccine doses, respectively. Seven of 9 patients who underwent LT had two doses of VZV vaccine. Six patients had seropositive before LT and persisted at 3 to 6 months after LT. Of 2 patients who received only one dose, TV was not detected after LT. Conclusions The two doses of VZV vaccine appeared to be more immunogenic than one dose in pediatric LT candidates aged less than 2 years.