Worldwide, hepatitis B virus (HBV) infection is a major cause of acute hepatitis,and chronic infection with HBV often leads to chronic hepatitis, liver cirrhosis,and hepatocellular carcinoma. So far, the most effective way to prevent HBV infection in susceptible population is to inject hepatitis B vaccine. However, long-term protection against hepatitis B virus (HBV) after vaccination remains widely debated. This study aims to evaluate the existence of immune protection in healthy children with negative hepatitis B surface antibody and find a method to evaluate the immune protection induced by hepatitis B vaccine.

One method to determine the long-term protection provided by hepatitis B vaccine against HBV infection is to estimate the cumulative incidence of chronic carrier status and breakthrough infection of previously vaccinated individuals in different periods. Up to now, no international standard suggests that hepatitis B vaccine should be used as a routine immunization program. However, it is an important issue to discuss the immune protection of healthy children with negative hepatitis B surface antibody and the duration of this protection in the future. Therefore, this study aims to evaluate the existence of immune protection of healthy children with negative hepatitis B surface antibody, find a method to evaluate the immune protection induced by hepatitis B vaccine.

The main content of the study: To recruit healthy children. Children lacking HBsAb were selected for immune memory test and receive a Hep B booster. The results of Antibody positive group and antibody negative group were compared and analyzed. To find out the most suitable method for evaluating immune protection.

Inclusion Criteria:

• Children who are 1-15 years old in Chongqing
• After birth, three injections of Hep B were inoculated in time according to the procedure of 0, 1 and 6 months(The vaccination certificate record)
• No HBV booster vaccine given since primary HBV immunization
• Children or guardian knew and agreed to accept the study
• Follow - up study and blood collection after vaccination can be accepted

Exclusion Criteria:

• Unwilling or impossible to participate in this research project;
• Have a history of allergy or have had a serious vaccine reaction
• Have immune impairment diseases and appear immune impairment;
• Immunosuppressive treatment, receive any injection or oral administration of cortisone or cancer chemotherapy;
• Any kind of vaccine or any kind of observation drug has been vaccinated in the past four weeks;
• Any acute disease or other infection requiring antibiotic or antiviral treatment in the past four weeks;
• Fever symptoms occurred in the past week ( axillary temperature ≥ 38 °C)
• Blood transfusion experience;
• Has a history of more serious infectious diseases ( five types of hepatitis, AIDS, syphilis, gonorrhea, etc. );
• Hepatitis B infection or carriers(lineal relationship);
• Abnormal physical examination

Healthy Children Aged 1-15 in Chongqing