The aim of the study is to assess the impact of the current vaccination strategy in the Netherlands and how it can be improved. To investigate that, first the fraction of asymptomatic cases will be determined and the differences in viral load during the acute and chronic phase of HBV infection will be determined. The effect of changes in sexual risk behavior will also be taken into consideration. Epidemiologic and phylogenetic analysis will be used along with mathematical modeling of the HBV epidemic to answer the following research questions: 1. How does viral load (and infectivity) change with the progression from acute to chronic hepatitis B? What fraction of new HBV infections can be attributed to chronically versus acutely infected patients?2. What fraction of HBV infected patients is a-symptomatic? Does the viral load differ between symptomatic and a-symptomatic HBV patients?3. What is the effectiveness of the current risk group vaccination strategy against HBV in the Netherlands, reflected by changes in incidence, transmission patterns, and circulating virus strains?4. How long should the existing vaccination policy be continued until it becomes successful? What other policies could be equally (or more) successful and in what time-frame?
Of the estimated 2 billion people ever infected with the hepatitis B virus (HBV) worldwide, over 350 million are currently chronically infected. These chronically infected persons are at high risk for cirrhosis and cancer of the liver, diseases that kill over an estimated million people each year. Therefore the WHO recommended universal vaccination for all countries in 1997.In 2002, a risk group vaccination program against hepatitis B was implemented in the Netherlands and not a universal vaccination program which was implemented by most western countries.The objective of this multidisciplinary proposal is to assess the effectiveness of the targeted vaccination program against hepatitis B in the Netherlands, reflected by changes in incidence, transmission patterns, and circulating virus strains. We also want to assess how long the existing vaccination policy should be continued until it becomes successful and what other policies could be equally (or more) successful, and in what time frame.Epidemiologic, phylogenetic, coalescent, and cluster analysis will be used along with thorough mathematical modeling of the HBV epidemic to answer these questions. In order to come to such a thorough model, it is necessary to gain more insight in the actual input of chronic infections in hepatitis B transmission and the proportion and input in hepatitis B transmission of a-symptomatic patients. In this way we can assess the number of new HBV infections prevented by vaccination and the effect of changes in sexual risk behavior on HBV incidence. We will also be able to obtain a better insight in the forces driving the HBV incidence and estimate the effect of different prevention approaches. Several other countries in the world have a targeted HBV vaccination program, the answers to these questions are not only important for our own country but also for other industrialized countries with similar (adult) risk groups for HBV. |
