BACKGROUND & AIM:
Hepatitis B virus (HBV) infection was hyperendemic in Taiwan before the implementation of universal infant hepatitis B immunization program, which was launched in 1984. Five previous seroepidemiologic surveys were conducted at 0, 5, 10, 15, and 20 years after the launch of the vaccination program.
We enrolled 3,332 subjects younger than 30 years of age with approximately 100 in each age cohort. Subjects were recruited voluntarily from schools and other institutions in Taipei, as in previous surveys. HBV seromarkers, included hepatitis B surface antigen (HBsAg) and antibodies to HBsAg (anti-HBs) and to hepatitis B core antigen (anti-HBc). HBV DNA levels were determined in subjects that were anti HBc positive/ HBsAg negative (anti-HBc only).
The HBsAg, anti-HBs, and anti-HBc seropositive rates were very different between those born after the program in 2009 and the baseline group in 1984 (0.9% vs. 10%, 55.9% vs. 24.5%, and 7.0% vs. 28%, respectively). HBsAg prevalence further decreased in the vaccinated cohorts in this 6th survey. A positive maternal HBsAg status was found in 86% of vaccine failures. Serum HBV DNA was detected in 4.2 % (6/142) of anti-HBc positive/ HBsAg negative subjects with a low level of HBV DNA. All of these six subjects' HBV were genotype C.
The universal infant HBV immunization program in Taiwan has completed its 25-year follow-up and its efficacy in young adults is clear. The continued decrease in HBsAg prevalence suggests that the elimination of HBV infection is becoming a reality.