Persistence of anti-HBs and immunologic memory in children immunized with hepatitis B vaccine

Background: We aimed to examine the persistence of an-HBs in Bangladeshi children aged 5 and 10 years a�er primary vaccina�on, and this response to a booster dose. Methods: A total of 100 children were enrolled who were divided into two groups (A and B). Group A comprised of 50 children vaccinated 5 years ago, and group B had 50 children vaccinated 10 years ago. Hepa��s B surface an�body �ter was measured, and a booster dose of the vaccine was administered to those who had an-HBs less than 10 mlU/ml. Seventeen such children from group A and 27 from group B were vaccinated with a booster dose. A�er one month, 12 children from group A and 18 children from group B were retested for hepa��s B surface an�body levels. Results: A�er 5 and 10 years of primary vaccina�on, 66.0% and 46.0% children had protec�ve an�body levels. A�er one month of booster dose, 91.6% children responded to the increased level of an-HBs in group A. Among them, 66.6% showed an adequate response. In group B, 88.8% had an increased level of an-HBs an�body where 83.3% had an adequate response. Geometric mean �tre of an-HBs an�body boosted by 35 and 75 �mes from pre-booster �me to post-booster vaccina�on in group A and B, respec�vely. Conclusion: Children had protec�ve levels of an-HBs an�bodies at 5 and 10 years a�er comple�on of the primary vaccina�ons. Anamnes�c response to booster vaccina�on conﬁrmed the persistence of an eﬀec�ve immunological memory in vaccines.


Hepatitis B virus (HBV) infection is
In 1992, the global advisory group of EPI at World Health Assembly recommended introduction of HBV vaccine into national immunization programs for countries with a hepatitis B carrier rate of 8% or greater by 1995 and in all countries by 1997. 4 The EPI schedule of vaccines is three doses at 6, 10, and 14 weeks of age in Bangladesh. Vaccine-induced serum concentration of anti-HBs 10 mlU/ml has been considered as protective level in several studies. 5 Undetectable or declining anti-HBs levels are not unusual. Long-term observation of

Persistence of anti-HBs and immunologic memory in children immunized with hepatitis B vaccine
Results: A er 5 and 10 years of primary vaccina on, 66.0% and 46.0% children had protec ve an body levels. A er one month of booster dose, 91.6% children responded to the increased level of an -HBs in group A. Among them, 66.6% showed an adequate response. In group B, 88.8% had an increased level of an -HBs an body where 83.3% had an adequate response. Geometric mean tre of an -HBs an body boosted by 35 and 75 mes from pre-booster me to post-booster vaccina on in group A and B, respec vely.
Conclusion: Children had protec ve levels of an -HBs an bodies at 5 and 10 years a er comple on of the primary vaccina ons. Anamnes c response to booster vaccina on confirmed the persistence of an effec ve immunological memory in vaccines.

BRIEF ARTICLE
vaccinated newborns revealed that anti-HBs become low or negative in 15%-50% among the vaccine responders within 5 to 10 years. 6 However, long-term protection may exist despite decreasing level of anti-HBs antibodies over time. It is due to the priming of memory cells, which can create a memory (anamnestic) response when challenged. 7 So, the study aimed to evaluate the persistence of anti-HBs five and ten years after primary vaccination by EPI schedule, and also to see anamnestic reaction in those with a declining level of antibody to determine whether or not a booster dose is needed in Bangladeshi Children. A structured questionnaire was constructed, and data were collected by the researchers of this study. All ethical issues were discussed with the parents and they were clearly informed in an easily understandable local language about the nature and purpose of the study, procedures followed, risks associated with it, benefits, and their right to participate or withdraw from the study at any time. Then, a written informed was obtained from parents and every caution was taken so that no harm could be caused to the cases. Detailed history regarding age, sex, anthropometry, blood transfusion, history of infected parents, family history of contact with HBV, any surgical or dental procedure, hepatitis B vaccination, and the number of doses were recorded. Anthropometric records, height, and weight were kept for each child. Two ml of venous blood was collected, and samples were tested on the same day for 2. The high anamnestic response rate after the booster dose denotes the existence of immunologic memory.

This
3. The persistence of immunogenicity of the HBV vaccine is recommended to be studied for more extended periods of time to detect the need for a booster dose in adolescence or early adulthood.
with an increased level of anti-HBs. Sixteen (88.8%) children in group B also responded with an increased level of anti-HBs (TABLE 1).
In both groups, children with weight for age percentile (WAP), height for age percentile (HAP) and BMI lie below the 5th percentile had low seroprotection rate than normal children, though findings were not statistically significant (  vaccination (FIGURE 1).

DISCUSSION
The present study showed that the anti-HBs titer between children tested at 5 and 10 years studies. [10][11][12][13] In this study, nutritional status of both groups was compared in relation to antibody response. Children with weight for age percentile (WAP), height for age percentile (HAP) and BMI for age lies below the 5th percentile in both groups who had less seroprotection rate than normal children, though findings were not   The present study showed that 17 (34%) and 27 (54%) children lost protective levels of antibodies at 5 and 10 years after primary vaccination, but in majority of them, the immunological memory remained intact. Banatvala et al. 6 reported that those individuals who were vaccinated in the past and whose level of anti-HBs declined to low or undetected levels over time, can climb an anamnestic reaction within a time as short as 4 days of viral exposure.

Conclusion
The study acknowledges certain limitations, with one of