Long-term Kinetics of Hepatitis-B Vaccine Induced Antibody

Hepatitis B is a viral infection of the liver. About 350 million people worldwide are ardent carriers of the Hepatitis B virus (HBV). The infection, if not properly checked, can cause acute and chronic liver disease including cirrhosis and hepatocellular carcinoma (HCC). The aim of the study was to assess the persistence of hepatitis B antibody after vaccination through a fitted model and use the model to monitor the persistence of the antibody for long time. Fractional polynomial of time was used in fitting linear mixed model with inclusion of random effects in order to account for generally known risk factors and the unknown individual characteristics that influence the antibody titre level. The mean anti-HBs was found to be a function of time and body mass index. The model shows that there is sharp decrease in the mean anti-HBs a month after vaccination and this decline was gradual thereafter. Two percent was found to have a titre level below 10 IU/L while the rest 98% has between 10 IU/L and 100 IU/L in the first five years after vaccination. This ratio changed a bit within 5 to 10 years and further to 4% and 96% respectively. After the fifth year, the ratio changed slightly to 9%, 28% and 63% respectively. It was established that there is strong evidence of immunity in form of long - term persistence of antibody in the volunteers as a result of the vaccination, confirming the efficacy of the vaccine and therefore, there is no need for revaccination.