Humoral Immune Response to HBV Vaccination Post-Chemotherapy in Pediatric Oncology Patients

Abstract

Background: Hepatitis B virus (HBV) infection remains a global public health problem. Despite Egypt is considered a region of low endemicity and with the implementation of the national vaccination strategy since 1992, it is anticipated to remain a public health burden especially with the recent waves of migration. Objectives: To evaluate the effect of chemotherapy on humoral immunity to HBV vaccination and reevaluate the effect of double booster dose of HBV vaccine in protecting the children against the immune-suppressive effect of chemotherapy. Subjects: 150 Egyptian children and adolescents with newly diagnosed acute lymphoblastic leukemia and acute myeloid leukemia, with confirmed HBV vaccination were initially screened. Sixty cases were excluded due to shifting to another hospital or lost follow-up. Ninety patients were recruited before commencing chemotherapy. Of those, sixty patients were consented to receive a booster dose of HBV vaccination. Methods: Before initiation of chemotherapy, all patients underwent assessment of liver function tests (LFTs) and quantitative determination of HBsAg and anti-HBs. Quantitative real time PCR was used to detect of HBV viremia, in ten patients. After the induction phase of chemotherapy patients reevaluated clinically and had their LFTs and quantitative determination of anti-HBs reassessed. Results: Fifty-four (60%) children were found to be seronegative for HBsAg at diagnosis of leukemia. Of the 90 studied children, 32 (35.6%) had no protection with anti-HBs titres <10 IU/L, 44 (48.8%) had a level between 10 and 100 IU/L and 14 (15.6%) had protective titres >100 IU/L. Real time PCR detected HBV DNA in 60% of sero-negative patients. Chemotherapy significantly decreased (P=0.0118) the anti-HBs titre in patients who did not receive the booster vaccine with decrease of the mean anti-HBs titter from 141±270 IU/L to 24±75.5 IU/L. When a booster double dose of HBV vaccine was given to sixty children, the anti-HBs titer was significantly increased (P=0.0008), with increase of the mean anti-HBs titer from 51±81 IU/L to 149±210 IU/L. Conclusion: Despite the implementation of obligatory vaccination against HBV only 40% of children were HBsAg positive. A booster double dose of HBV vaccination before initiation of chemotherapy protects children against negative impact of chemotherapy. Keywords: HBV infection, HBV vaccination, ALL, acute lymphoblastic leukemia