Evaluating the Association between HBV Vaccination Coverage and the Incidence of Liver Cancer at a Global Level

Abstract

Background: Liver cancer today is the second most common cause of cancer-related death and ranks sixth most incident cancer worldwide. The most prevalent histopathological type of liver cancer is hepatocellular carcinoma (HCC). The most common cause for HCC is HBV, and it contributes to 50%-80% of HCC around the world. HepB vaccine was introduced in 1982 and incorporated to the Expanded Programme of Immunization (EPI) in 1992. The vaccine has proven to be associated with a reduced liver cancer incidence in studies from Taiwan, The Gambia and China. We aim to study the same association at a global level Methods: We collected data on HepB vaccine coverage for children less than 1-year old for 195 countries from the WHO, reported in percentages for every year starting from 1989 to 2013. We also collected data on liver cancer incidence rates for 5-year age groups (starting from 5-9) for 188 countries from the Institute of Health Metrics and Evaluation (IHME) reported in number of cases per 100,000 population for every year from 1980 to 2013. We created overlapping, consequent 5-year HepB vaccine coverage rates from the WHO data, calculated the median for each and matched with the respective cohort in the IHME data. For the statistical analysis, we chose the generalized linear latent and mixed model (GLLAMM). We used Microsoft Excel, R and Stata for our data management and analysis. Results: Overall, we had 2,129 birth cohorts form 153 countries. All observations were in 5-year age groups (5-9, 10-14, 15-19 and 20-24). Among 5-24 years, higher 5-year median vaccination coverage rates by 10% were associated with a relative risk that is lower by a factor of 0.948 cancer incidence after adjusting for age group and year of observation (95% CI: 0.916, 0.982). Conclusion and recommendation: Higher HepB vaccine coverage rates were associated with lower liver cancer incidence rates. We recommend that future studies evaluate this association at older age groups in order to demonstrate a larger effect size.