Nationwide vaccination: a success story in Taiwan.

In the early 1980s, 15-20% of the population of Taiwan were estimated to be hepatitis B virus (HBV) carriers. A programme of mass vaccination against hepatitis B was therefore launched in 1984. In the first 2 years, newborns of all HBVsurface antigen (HBsAg)-positive mothers were vaccinated. Since 1986, all newborns, and then year by year pre-school children, primary school children, adolescents, young adults and others have also been vaccinated. Vaccination coverage is over 90% for newborns, with 79% of pregnant women screened for HBsAg. The proportion of babies born to highly infectious carrier mothers who also became carriers decreased from 86-96% to 12-14%; the decrease was from 10-12% to 3-4% for babies of less infectious mothers. Between 1989 and 1993, the prevalence of HBsAg in children aged 6 years also fell from 10.5 to 1.7%. The average annual incidence of hepatocellular carcinoma in children aged 6-14 years decreased significantly from 0.7 per 100,000 in 1981-1986 to 0.36 per 100,000 in 1990-1994 (P<0.01). Similarly, the annual incidence of hepatocellular carcinoma in children aged 6-9 years declined from 0.52 per 100,000 for those born in 1974-1984 to 0.13 per 100,000 for those born in 1986-1988 (P<0.001). The mass vaccination programme is highly effective in controlling chronic HBV infection and in preventing liver cancer in Taiwan. If a coverage rate of 90% of all newborns vaccinated against hepatitis B can be maintained, by the year 2010 the carrier rate in Taiwan is expected to decline to <0.1%.