Molecular Characterization of Hepatitis B Virus Isolate from a Vaccinated Child in Ogbomoso, Oyo State, Nigeria

Background Hepatitis B virus (HBV) infection remains a global health challenge, particularly in Sub-Saharan Africa, where genotype E predominates. Despite vaccination programs, breakthrough infections continue to be reported. Aims and Objectives This study characterizes HBV isolated from a vaccinated child in Oyo State, Nigeria, who tested positive for HBsAg by ELISA. Methodology Out of 336 children participating in the vaccine impact study, 4 (1.2%) tested positive for HBsAg. The four samples were then subjected to qPCR, but only 2 showed detectable viral load by qPCR. For these two, the HBV gene was amplified; one of the amplicons was undetectable. Whole genome sequencing was performed on the detectable HBV gene amplicon from the study sample, followed by nucleotide and amino acid sequence analysis. Results Bioinformatic analyses identified the isolate as genotype E with no mutations linked to vaccine escape. Conclusion The findings highlight challenges in preventing vertical transmission of HBV, underscoring the need for enhanced antenatal screening and timely immunoprophylaxis in endemic settings.