Long-Term Hepatitis B Vaccine Immunity in Ethiopian Children That Received a Pentavalent Vaccine Series: A Retrospective Cohort Study.

Our study showed markedly low vaccine-induced hepatitis B surface antibody levels among the study population, especially adolescents. The presence of breakthrough infections may suggest a genuine lack of response and not just a mere drop in antibody titers and thus could highlight a significant public health problem in Ethiopia. Further immunologic studies and a thorough analysis of vaccine storage and administration should be conducted to inform prevention programs.