| BackgroundsHepatitis B, an infectious disease caused by HBV, harms the people's health seriously in china currently. There are still some controversies about the necessity and proper time to launch re-immunity and booster immunization of Hepatitis B vaccine. While no relative policies about that issue have been made out in China today. This study focus on the teenagers who had only received the fundamental immunity of HBV vaccine before and then accepted the booster immunization of Hepatitis B vaccine in Changshan county of Zhejiang province to observe the indicator of positive conservation rate and the characteristics of anti-HBs recall action. Based on those results, an accession of the effects of Hepatitis B vaccine re-immunity and booster immunization was performed to determine the advanced and reasonable preventive measures of the Hepatitis B vaccine booster immunization for juveniles in the future.Materials and MethodsUsing uniform investigation and registration forms, the epidemic prevention personnel of Qingshi and Zhaoxian towns screened out 1534 teenagers aged between 5 to 16 years old who hand only received basic Hepatitis B immunity in neonatal period from Zhaoxian town (760 individuals) and Qingshi town (774 individuals) of Changshan county as the study objects according to unified criteria for inclusion and exclusion in study fields in this research.6 certified investigators who had been trained by the CDC of Changshan county delivered the uniform questionnaires (survey items including objects' registry number, parents' names, name, gender, birth date, present and past history of Hepatitis B, history of immunization of Hepatitis B, home address and so on) provided by the CDC of Zhejiang Province to every object in fields to collect relative information.1500 certified questionnaires were obtained and the corresponding individuals who were primarily selected, accepted the baseline serological examination of Hepatitis B, containing 3 indices, HBsAg, anti-HBs, anti-HBc, with 3ml venous blood of the objects surveyed before reimmunization and booster immunization. For unadequate volume of some blood samples,1434 blood samples were examined from all the1500 samples collected actually.17 teenagers were excluded for the positive HBV surface antigen after screening test of 3 judging criteria of HBsAg, anti-HBs and HBcAb before re-immunity and booster immunity. These 1417 teenagers certified accepted the re-immunity and booster immunity with Hepatitis B vaccine. During this study 135 persons losted in follow up for the reasons of transfer to another schools or illness and 1282 candidates rested finally.764 objects with both negative HBsAg and anti-HBs accepted re-immunity; 518 objects with negative HBsAg and positive anti-HBs got booster vaccination.During the 764 objects reimmunized,374 teenagers from Zhaoxian town and 390 individuals from Qingshi town accepted 5μg yeast-derived Hepatitis B vaccine (produced by Shenzhen Kangtai biological products Ltd. with standard of 0.5ml per injectionbottle and batch number of 20071223-7) and A Hepatitis combined B vaccine (containing 5μg HBsAg per injectionbottle and produced by Beijing Kexing Company with standard of 0.5ml per injectionbottle and batch number of 2009040302) respectively.3ml venous blood everybody was collected to examine the content of anti-HBs titer one month later of the first and thirst vaccinal injection separately to evaluate the effects of re-immunization.During the 518 objects who had been booster immunized,257 teenagers from Zhaoxian town and 261 individuals from Qingshi town accepted the vaccine of 5μg yeast-derived Hepatitis B vaccine (produced by Shenzhen Kangtai biological products Ltd. with standard of 0.5ml per injectionbottle and batch number of 20071223-7) and A Hepatitis combined B vaccine (containing 5μg HBsAg per injectionbottle and produced by Beijing Kexing Company with standard of 0.5ml per injectionbottle and batch number of 2009040302) separately.3ml venous blood everybody was collected to examine the content of anti-HBs titer after one month and seven months of the first injection of booster vaccination separately to evaluate the effects of booster immunization.All the research objects from Zhaoxian town and Qingshi town were exerted the first vaccinal injection from 23 and 24 in september of 2009 separately. The Hepatitis B vaccines were provided by the center of disease prevention and control of Zhejiang Province. Hangzhou Aidikang Company was authorized for the detection work of the content of anti-HBs quantitatively with the method of chemiluminescence and with the reagents produced by Yapei Company. The result of anti-HBs≥10.0 mlU/ml was defined as positive. The conclusion was inferred by the data analysis of Chi square, rank sun test and other statistical methods.ResultsEffects of re-immunityAfter one time injection of re-immunity, the positive conservation rate of anti-HBs reached 90.58%, ranging from 76.09% to 99.02%, and the older teenager was the lower level rate she/he obtained. There were significant differences of the rate of anti-HBs in various age groups(x2 trend=70.03, p<0.05); the median of anti-HBs titer differences between the original period and the period after re-immunity ranged from 97.9 to 571.7mlU/ml. The lower level of the rising range of titer was, the older teenagers were (x2=83.84, p<0.05). After three times injection re-immunity, the positive conservation rate of anti-HBs approached 99.08%, children aged 5 to 12 years with the rate of 100%; the median of the difference of anti-HBs titer value between the previous period and the period after re-immunity ranged from 553.0 to 707.8mlU/ml. No significant differences of titer rising range were found among various age groups, the results of anti-HBs conservation rate and the rising range of antigen titer were both better in 3 times injection of re-immunity than that of 1 time treat.The positive conservation rate of anti-HBs and the rising range of anti-HBs titer both had some relationships with the aspects of injection times of re-immunity, species of Hepatitis B vaccine and age of objects. After one time injection in re-immunity, the positive conservation rates of anti-HBs with 5μg Hepatitis vaccine and A hepatitis combined B vaccine were 88.24%, ranging from 75.0% to 100%, and 92.82%, ranging from 72% to 100% respectively. The positive conservation rates of anti-HBs of latter was higher than that of former with statistical differences (χ2=4.70, P<0.05). The two kinds of vaccines referred before both showed the trend that anti-HBs positive conservation rate decreased with the increase of age gradually. After 3 times injections re-immunity of 5μg Hepatitis vaccine or A hepatitis combined B vaccine, anti-HBs positive conservation rate both ranged from 92% to 100%. The median of anti-HBs titer differences between the original stage and the stage after one time injection re-immunity of 5μg Hepatitis vaccine or A hepatitis combined B vaccine ranged from 94.6 mIU/ml to 624.8 mIU/ml, with significant differences of the median of anti-HBs titer differences among various age groups. While these two kinds of vaccines both showed no statistical differences of anti-HBs titer change among all the various age groups after tree times injection re-immunity.Effects of booster vaccinationThis study showed good recall reaction of anti-HBs, and the anti-HBs titer increased quickly and obviously with booster vaccination. The median of anti-HBs titer difference between the previous period and the period after booster vaccination achieved 3583 mIU/ml and 572.2 mIU/ml after one month and seven months respectively. The titer values of anti-HBs both after one month and after seven months of booster vaccination were different significantly among various age groups, and the rising range was higher in younger age groups(P<0.05).The anti-HBs titer values altered significantly among different age groups after one month of booster vaccination both in group A,5μg Hepatitis vaccine injection, and in group B,A Hepatitis combined B vaccine injection. The rising range of titer reached higher level in younger objects than that in older ones in different age groups in group A. The highest and lowest levels of rising ranges appeared in 11～years old group and 15～16 years old group separately in group B.The declined percentages of anti-HBs titers were different among various age groups, which were different either in the groups A or in the groups B. The indices mentioned in various age groups ranged from 70.45% to 91.13%, the most fast decline of this index existed in 11～years old group and the most slow decline in 15～16 years old group in group A, and in 15-16 years old group and 11-years old group correspondingly in group B.ConclusionsBased on the destination of evaluation about the effects of Hepatitis B vaccine re-immunity and booster immunization, we can infer that the effects of 3 times injection re-immunity is preferable than 1 time disposition both in the indices of anti-HBs positive conservation rate and the rising range of antigen titer. The children aged 12 years or younger can obtain 100% anti-HBs positive conservation rate with the 3 times injection re-immunity. The anti-HBs positive conservation rate and rising range of antigen titer of re-immunity are related with the factors of injection times, species of Hepatitis B and the age of objects studied. After the booster immunity, it shows perfect recall reaction of anti-HBs, with fast and obvious increase of antigen titer values, and then the titer value falls after rise quickly after 7 months of booster vaccination, while still higher than that of the period before booster immunity. Descending rate of anti-HBs titer among various age groups are different after booster vaccination, and the descending rates between 5μg yeast-derived Hepatitis B vaccine and A Hepatitis combined B vaccine are also different.
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