Study on immunity against Hepatitis B in children after vaccination during infancy

Abstract

INTRODUCTION AND OBJECTIVES: Hepatitis B vaccine is given in Sri Lanka to all infants at 2, 4,6 months. As a low prevalent country the risk of acquiring Hepatitis B is more likely during adolescence and later. It is important to know whether immunity produced by vaccination during infancy last up to this stage, or a booster dose is needed to augment the immune response. METHOD: With informed written consent and assent from children, 150 ten year old school children with evidence of Hepatitis B vaccination during infancy, were tested for Hepatitis B antibody status using ELISA. Children who had an antibody titre less lOmlU/mL were offered a free booster dose. Antibody levels were retested one month after the booster. RESULTS: 128 (67%) had an antibody titre above 10m ID/ml. All children with a titre <10mlU/ml, accepted the booster dose. All children who received the booster had an antibody response above 10mlU/l, while (72%) had a titre >100mlU/l. CONCLUSION: Vaccination against Hepatitis B during infancy appear to produce protective level of antibodies at ten years of age. Even the children with antibody titres below protective level produced a sharp rise in titres with a booster dose. As this response could be expected with a natural infection, booster dose to augment the immune response produced by vaccination during infancy is not needed.