Immunogenicity of varicella zoster vaccine in pediatric liver transplantation

Background: Pediatric liver transplant (LT) candidates often miss complete varicella-zoster virus (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 persistence of its 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 between 1 to 3 months later, and at least 4 weeks before LT. Varicella-zoster IgG (VZG) was used to detect immunoglobulin G antibodies to VZV and was reported as a test value (TV). A test value ≥ 0.9 was considered as seropositive. TV was measured at enrollment, 1 month after the first and the second dose of VZV vaccine, before LT, and 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 months (IQR 9-12) and 13 months (IQR 12-33), respectively. The seroconversion rate was 66.7% (8/12) and 70% (7/10) after the first and second VZV vaccine doses, respectively. Seven of nine patients who underwent LT had two doses of VZV vaccine. Six patients were seropositive before LT, which persisted at 3 to 6 months after LT. Of two 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.