The Prevalence and Its Meaning of Anti-HBc alone 15 Years Subsequent to Mass Hepatitis B Vaccination

　　　　　臺灣在B型肝炎全面疫苗接種15年後，已大幅降低B型肝炎之感染率與帶原率。單獨B型肝炎核心抗體存在（即核心抗體陽性、表面抗原陰性、表面抗體陰性）之意義與盛行率在疫苗接種世代則未知。我們以雲林臺西國中青少年疫苗接種世代為研究對象，採用檢測e抗體、疫苗補接種探究免疫記憶、以實時間定量聚合鍊鎖反應檢測病毒量等多重方式，來決定單獨B型肝炎核心抗體存在之意義。該鄉之青少年於嬰兒期之疫苗接種率為72.4%（312/431），B型肝炎感染率（核心抗體陽性）與帶原率（表面抗原陽性）分別為195%（219/1，126）與7.1%（80/1，126）。單獨B型肝炎核心抗體存在盛行率為0.9%（10/1，126）。在這10位單獨B型肝炎核心抗體存在之青少年，5位e抗體陽性；其中3位有免疫記憶，另2位無免疫記憶者視為帶原者（1位血中可偵測到病毒；28l copies/mL）。1位e抗體陰性且無免疫記憶者，接種三劑疫苗後，表面抗體轉陽；故核心抗體推論為假陽性。1位追蹤核心抗體呈陰轉，故核心抗體亦為假陽性。其餘3位單獨B型肝炎核心抗體之意義無法確定。單獨B型肝炎核心抗體存在之盛行率在疫苗接種世代只有0.9%；有一半的單獨核心抗體存在代表曾受感染，其中1位更可以在血中偵測到病毒。
　　　　　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.