Effect of Population-Wide Hepatitis B Vaccination in Preventing Liver Cancer Among Children and Young Adults in the United States

Abstract

Background: Liver cancer is the second most common cause of death from cancer worldwide1. In 2013, 79,2000 new cases of liver cancer and 818,000 deaths occurred globally2,3. Chronic infection with HBV accounts for at least 50% of liver cancer globally4. In the United States (US), liver cancer constitute the ninth leading cause of cancer death. The incidence of the cancer has persistently increased in the recent decades. Universal HBV vaccination was introduced in 1992 in the US. However, incidence trends of liver cancer among US children is poorly researched or relevant studies are not up-to-date5. Aim: This study aims to explore the effect of HBV population-wide vaccination program in reducing liver cancer incidence in the vaccinated children and adolescents in the US. Methods: Liver cancer incidence data were obtained from Cancer Incidence in Five Continents (CI5) databases (volumes I to X) from International Agency for Cancer Research (IARC). Data acquisition and analysis covered available incidence data between 1978-2007 from 9 cancer registries from Surveillance, Epidemiology, and End Results Program (SEER) from the US presented in the CI5 databases. Age-specific incidence rates of liver cancer (based on 5 year age groups ie 5-9 year, 10-14 year and 15-19 years) were calculated using age and sex-disaggregated incidence and population data from the SEER cancer registries. Stata software version 14.0 (StataCorp, USA) was used to calculate age-specific incidence rates, using number of liver cancer incident cases in each age group by the number of population in the respective age group. Age-specific rates were analyzed by period of diagnosis and by birth year. Rate ratios were estimated from age-group-specific Poisson regressions. Results: A total of 140 liver cancer incident cases were registered in the 9 SEER registries between 1978 to 2007 in the US. The incidence rate of liver cancer in children 5 to 9 years of age from 1978-1982 was 0.10 per 100,000 children. The incidence increased to 0.16 for the period from 2003-2007. The same trend is seen for the age group 10-14 and 15-19 years of age. Overall, age-specific incidence rates for liver cancer increased across age groups of 5-9, 10-14 and 15-19 year in the population covered by the 9 SEER registries in the US. However, risk estimates (incidence rate ratios, resulted from age-group-specific Poisson regressions did not show statistical significant effects. Conclusion: While the global response to implement population-wide HBV vaccination program is out of question, efforts to establish processes to evaluate the effect of such programs seems to be incomparably limited. Estimating the effect of HBV vaccination will relatively improve with time as further incidence data become available eg upon publication of data from new volume of CI5 databases.