Hepatitis B virus is highly infectious and remains a global health problem. Worldwide, approximately 2 billion people have been infected with hepatitis B virus, and 400 million of them are chronic carriers of the virus.(1) The infection causes significant morbidity and mortality, ranging from acute or fulminant hepatitis to end-stage liver disease and hepatocellular carcinoma.(2, 3) Hepatitis B virus infection is prevalent in Asia, Africa, Southern Europe, and South America, where the infection mostly occurs in the perinatal period or early childhood, and the prevalence of hepatitis B surface antigen (HBsAg) in the general population ranges from 2% to 20%. On the other hand, hepatitis B virus infection is less common in developed countries where the infection is contracted after childhood through horizontal transmission.(1, 3, 4)
Currently, hepatitis B virus infection can be controlled by immunizing at-risk individuals, interrupting the routes of transmission, and treating those who are chronically infected.(5) Among these measures, hepatitis B vaccination is the most effective and has been available for more than 2 decades. The World Health Organization recommended that hepatitis B vaccination be incorporated into routine infant and childhood Expanded Programs on Immunization for countries with hepatitis B virus carrier rates >8% by 1995 and for all countries by 1997.6 By the end of 2003, 147 countries had included hepatitis B vaccine in their routine immunization schedules.
In recent decades, the heavy disease burden caused by hepatitis B virus infection has resulted in the creation of mass vaccination programs in many Asian countries. Taiwan’s program was launched in 1984. Among the earliest, it has shown great efficacy.(1, 7) In brief, a series of prevalence surveys on children born before and after implementation of the universal vaccination program revealed a remarkable decrease in the seroprevalence of HBsAg in Taiwan,8 with an overall effectiveness of ∼85% after implementation of the national vaccination program in 1984. Studies on the secular trend of liver disease also documented a 75% decrease in the incidence of hepatocellular carcinoma in children 6-9 years of age,9 and a 68% decrease in mortality from fulminant hepatitis in infants after launch of the universal vaccination program.10 The updated surveillance in 2004 further showed that the seropositive rates for HBsAg, anti-HBs, and anti-HBc were 1.2%, 50.5%, and 3.7%, respectively, in those born after implementation of the vaccination program.(11)
Therefore, universal hepatitis B vaccination can provide long-term protection for at least 20 years, and a universal booster is not indicated for the primary hepatitis B virus vaccinees before adulthood, as was observed in Taiwan. The successful hepatitis B vaccination program in Taiwan has been described before.12 Many other countries also have excellent performance.
Despite the success in many developing countries endemic for hepatitis B virus infection, vaccination against hepatitis B virus is often neglected in developed countries.
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– Jia-Horng Kao, MD, PhD, Ding-Shinn Chen, MD
This article was originally published in the December 2008 issue of The American Journal of Medicine.
