(Hepatology 2010;) Universal hepatitis B (HB) immunization has been implemented for more than 20 years in Taiwan and led to remarkable reductions in acute and chronic liver diseases.1, 2 The national immunization

program of Taiwan was launched in 1984: all neonates or infants born before Nov 1992 received plasma-derived HB vaccines at birth. They all received standard doses of HB vaccines at birth according to the same standard protocol. The coverage rate of HB vaccines during the past 2 decades in Taiwan has been >90% and data show that the national vaccine coverage rates were more than 95% in 2001 and 2002.3, 4 It has shown an efficacy of 78%-87% in decreasing the seroprevalence of hepatitis B surface antigen (HBsAg) carriage in all children,5, 6 a 75% decrease in the incidence of hepatocellular carcinoma among children 6-9 years of age,1 and a 68% decline in mortality from fulminant hepatitis and HB-related liver diseases in infants.2 Although this national vaccination program has been very successful, a gradual yearly decline in antibody titers against the HBsAg among vaccinees was noted in several follow-up studies.7-11 The antibody to HBsAg (anti-HBs) seropositivity

rate of the vaccinees decreased from 99% at 1 year to 83% at 5 years, 71.1% at 7 years, 37.4% at 12 years, and 37% at 15-17 years. The seronegative rate for three HB viral markers including HBsAg, antibodies to HB core protein (anti-HBc), and anti-HBs increased from 12.7% at 1 year to 62.6% at 15-17 years. Despite the effectiveness of buy U0126 HB immunization, natural HB infections were seen by detecting anti-HBc in 4.0%-5.7% of vaccine recipients in many studies.6, 10, 12 Case reports of vaccine failure have also been noted.13 The causes of

failure may be lower vaccination coverage and incomplete HB immunization in the early era of the nationwide HB immunization program or poor response to HB immunization, including vaccine failure.14, 15 Regarding immune memory to hepatitis B vaccination, Lu et al.16 found that breakthrough infections might occur 10 to 15 years later for children who initially had a low response to the HB vaccine. One or more PD332991 booster immunizations are needed in seronegative subjects 15 years after neonatal immunization with the plasma-derived HB vaccine. A recent study estimated that as high as 26.5% of fully vaccinated adolescents aged 15-18 years may have become immunologically naïve to the HB vaccine, raising concerns about the need for a booster vaccine for high-risk groups in the long run.7 An Alaskan study found that among children and adolescents vaccinated with HB vaccines during infancy there was an increased proportion of nonresponders among older adolescents, which may indicate waning immune memory.