Seroconversion of Hepatitis B Vaccine in Young Children in the Kassena Nankana District of Ghana: A Cross-Sectional Study.

BACKGROUND Hepatitis B Virus (HBV) infection is an important public health problem that requires high priority efforts towards prevention and control. Active immunization is the single most important and effective preventive measure against HBV infection. As a protective measure, Ghana introduced the mass immunization program against hepatitis B infection in children in 2002 in her Expanded Programme on Immunization (EPI). This study evaluated seroconversion (the point in time when the amount of antibody in the blood becomes detectable) and seroprotection (the point in time when the amount of antibody in the blood is enough to confer protection from the antigen that induced it production) status of children under this mass immunization program and measured their antibody levels five years after immunization. MATERIALS AND METHOD 200 archived plasma samples of children between the ages of 1-10 years were retrieved from a previous cross-sectional study by researchers from NHRC between 2009 and 2010. Of these, 104 have completed the EPI and were screened for HBsAg. Those found to be HBsAg-seronegative were stratified into three groups according to their age at which the last vaccine was administered. Their anti-HBsAg titer levels were estimated by enzyme linked immunosorbant assay (ELISA). RESULTS Two (1.9%) samples were HBsAg seropositive and were excluded from further analyses. 10 more samples were excluded from analyses because they were insufficient. The anti-HBs titers recorded ranged from 1.021 IU/L to 751.64 IU/L indicating a 100% seroconversion rate. In group one (0-6 months), 87.9% were seroprotected. Group two (2-3yrs) had 78.3% seroprotection and group three (3-5yrs) had 41.7% seroprotection. There was no significant difference between group 1 and 2. However, there was a significant difference between group 1 and 3 (p = 0.0137) and between group 2 and 3 (p = 0.0390) respectively. There was no significant difference between male and female children. CONCLUSION All the children who received doses of hepatitis B vaccine at 6, 10 and 14 weeks in the immunization program seroconverted, but their levels of protection waned with increasing years. Booster doses are therefore recommended after 5 years.