Forecasting the declining rate of chronic hepatitis-B carrier status at a Taiwanese university: twenty years after implementation of an universal HBV vaccination program in Taiwan.

BACKGROUND Prior to the introduction of universal hepatitis B virus (HBV) vaccination in Taiwan in 1984, 15-20% of the general population were chronic HBV carriers. METHODS We forecasted and quantified the declining HBV carrier rate 20 years subsequent to the implementation of universal HBV vaccination in Taiwan. At a Taiwanese university, 28,763 freshmen tested for serum HBsAg level were divided into ten age cohorts by date of birth, from July 1976 to June 1986 inclusive. Comparisons of HBsAg carrier rates according to gender were examined with the Z test. Regression methods and a time series model were applied to our sample to forecast trends in changes to the HBsAg carrier rate for the next five years. RESULTS Regression analysis demonstrated a trend toward declining HBsAg-positive carrier rates. The HBsAg carrier rate for male students decreased from 16.8% (for those born between July 1976 and June 1977) to 2.2% (for those born between July 1985 and June 1986). The carrier rate for their female counterparts over the same period declined from 12.2% to 2.4%. The HBsAg carrier rate for male participants was significantly greater than that of their female counterparts for certain years during the test period. The results of time series analysis suggests the HBsAg carrier status rate will approach zero for students born after July 1987 (expected to enrol in the university in 2006). CONCLUSIONS Our data demonstrate that in order for the HBV carrier rate to approximate zero, universal vaccination programs need to continue for at least 21 years.