Antibody response against Hepatitis B virus after vaccination and seroprevalence of HBV in children in Addis Ababa, Ethiopia

ABSTRACT

Background: Around two billion people have been infected with HBV worldwide, and more than 240 million are chronic carriers. Vaccine introduction for HBV in children was officially launched by the WHO in 1980. Since then the vaccine response level has been determined in different countries. Since the introduction of the vaccine in Ethiopia in 2007, few studies have been conducted to assess the antibody response against the HBV vaccine. Objectives: The aim of this study is to determine antibody response against HBV after hepatitis B vaccination and assess the seroprevalence of HBV in children in Addis Ababa, Ethiopia. Methods: A cross-sectional study was conducted using a multistage probability sampling technique. Four hundred and fifty children between the ages of 5 and 8 living in Addis Ababa were enrolled. Socio-demographic characteristics were obtained through a structured questionnaire and three to four ml of blood was collected from each child. ELISA was performed to determine antibody levels against HBV. Results:The mean age was 7+1 (SD) years. Anti-HBs were detected in 54.3% (208/450) of children with a slightly higher proportion of protective level in females 98 (54.7%) than males 110 (53.9%). The overall vaccine coverage in our study was 85.1 %. The proportion of children with a protective level (>10 mIU/ml anti-HBs antibody) declined as the age of the child increased 52.6%, 60%, 43.5% and 37.1% at the age of 5, 6, 7 and 8 years, respectively. Seroprevalence of HBsAg was 0.4%, whereas seroprevalence of anti-HBc was 5.6%. Age was negatively correlated with the response level (p=0.001), whereas sex and history of HBV infection had no significant association. Age was also significantly associated with seroprevalence of anti-HBc (p=0.003). Conclusion: The HBV vaccine coverage in children was high but antibody response against the vaccine appears low. Seroprevalence of the virus was also low. The low response level to the vaccine should be a concern and revaccination or booster doses should be considered for non-responding children. Further studies should also be undertaken