Cancer prevention by vaccination against hepatitis B.

Chronic inflammation caused by persistent infection is closely related to a number of cancers; these include hepatitis B (HBV) or C and hepatoma, human papilloma virus and cervical cancer, and Helicobacter pylori and gastric cancer. The first evidence of cancer prevention by vaccination in humans was provided by HBV vaccination in infants. Chronic HBV is related to approximately 60%-90% of hepatocellular carcinomas (HCC) in adults and nearly 100% of childhood HCC in areas endemic for HBV infection. The first universal HBV vaccination program was launched in Taiwan and has continued for more than 20 years. Three or four doses of HBV vaccine were given to all infants starting from the first week of life. In addition, infants of high-risk mothers (with positive hepatitis B e antigen or high HBsAg titers) were given hepatitis B immunoglobulin within 24 h after birth. At 20 years after the launch of the HBV vaccination program in Taiwan, chronic HBV infection (HBsAg seropositive) rates in the general population below 20 years of age have revealed a remarkable reduction from 10%-17% before the vaccination program to 0.7%-1.7% after the program. HCC incidence rate in children 6-14 years old also fell from 0.52-0.54 to 0.13-0.20 per 100,000 (R.R. = 0.25-0.36). HCC prevention failure is mainly related to vaccine failure to prevent chronic HBV infection. The causes of vaccine failure have included intrauterine infection, vaccine escape mutants, genetic hyporesponsiveness, and poor compliance. Future efforts to reduce vaccine failure will improve the efficacy of liver cancer prevention by HBV vaccination. The experience of HCC prevention by HBV immunization may be applied to the prevention of other infection-related cancers.