Hepatitis B vaccination and liver cancer mortality reduction in Korean children and adolescents

Liver cancer is one of the three most common causes of cancer mortality in the world and it is closely related to chronic hepatitis B viral(HBV) infection in Korea. The decline of HBV prevalence for the last two decades in Korea might be partly due to the HBV vaccination which was implemented as a national program starting in 1995. The aim of this study was to assess the period effect of the national HBV vaccination on liver cancer mortality in a young population. We compared age-specific mortality rates of liver cancer before and after the national vaccination program in the Korean population under the age of 20. To reduce year-to-year fluctuations in mortality, calendar years and age groups were divided into 4-year strata and the mortality rates were calculated for each stratum. Period effects of the national vaccination program were analyzed using age-period-cohort modeling. A total of 370 liver cancer mortality cases were identified during the period from 1991 to 2006. The period effect of the national vaccination program for the period 2002-2006 had a significantly reduced liver cancer mortality rate when compared to the period 1991-1994 when the national vaccination program was not implemented (RR 0.30, 95% CI 0.21 ~ 0.44). After implementation of the national vaccination program, HBV prevalence in Korean declined from 6~8% to 2~3%. This study demonstrates that the national vaccination program has contributed to the reduction of liver cancer mortality beyond just a natural decrease in Korean children and adolescents.