The prevalence and its meaning of anit-HBc alone 15 years subsequent to mass hepatitis B vaccination

Fifteen years subsequent to nation-wide mass hepatitis B vaccination program, the prevalence of anti-HBc and HBsAg among adolescents/children in Taiwan has decreased. The significance of anti-HBc alone among the vaccinees-cohort has not been determined as yet. The aims of this study were to investigate the prevalence and its meaning of anti-HBc alone among vaccinees-cohort based upon a battery of strategies, including evaluating the response to the hepatitis B vaccine booster, assessing tests for anti-HBe, and determining the viral load by use of a sensitive real-time polymerase chain reaction assay. Adolescents born after mass vaccination program being instituted and aged between 12 and 15 years in one rural township of Taiwan were selected as the studied population. The vaccination coverage rate during infancy was 72.4% (312/431). The seroprevalence of anti-HBc and HBsAg was, respectively, 19.5% (219/1,126) and 7.1% (80/1,126). The prevalence of anti-HBc alone was 0.9% (10/1,126). Five of these ten anti-HBc alone subjects were positive for anti-HBe; among them, three have anti-HBs anamnestic response after hepatitis B vaccine booster (ie, past resolved HBV infection), the other two without anti-HBs anamnestic response were thought to be HBV carrier (including one case with HBV DNA positive and viral load 281 copies/ml). One case that was negative anti-HBe result and had no anamnestic response was invited to complete HBV vaccination; and primary response was deduced. Therefore, anti-HBc of this case was assumed as false positive. Another one whose anti-HBc turned to be negative on follow-up sampling. Hence, his initial anti-HBc was also thought to be false positive. The last three complete vaccinated and negative anti-HBe cases could not be accurately differentiated as true positive as opposed to false positive. In conclusion, the prevalence of anti-HBc alone was 0.9% among vaccinees-cohort. One half of isolated anti-HBc subjects revealed that they were true positives, and viremia did occur for one case.