 The UK immunisation guidelines recommend that children immunised with an accelerated course of hepatitis B vaccine i.e. vaccination at 0, 1, 2 and 12 months receive an additional booster dose of vaccine in later childhood usually at 3 12 years of age. The primary objective of this study is to to assess what proportion of these children have protective concentrations 10mIUml of hepatitis B specific antibodies before and after the booster dose of hepatitis B vaccine. 