Survey of Anti-HBs Serum Level in Vaccinated ۷-۹ Year-old Children in Zanjan City ۲۰۰۴

Background: Vaccination against hepatitis B has lead to satisfactory production of anti-HBs in more than ۹۰% of the cases. Nevertheless, numerous studies have revealed a gradual decline in anti-HBs level. This study was carried out with the aim of determining anti-HBs serum level in ۷-۹ year-old children in Zanjan, vaccinated through routine nationwide vaccination program. Materials and Methods: Two hundred and seventy three students were selected through random multiple staged method from ۱۰ elementary schools in Zanjan. After getting the letter of satisfaction from parents and preparing ۵ ml blood sample, serum level of anti-HBs was determined using ELISA with Radium kit. All serums were also tested for anti-HBc. Data were categorized into four groups. The first group contained no antibody (۰) the second <۱۰, the third ۱۰-۱۰۰ and the forth >۱۰۰ unit/ml and serum level under ۱۰ was considered as weak response and confidence interval was estimated. Results: In ۲۹.۵% of the samples no anti-HBs was observed. In ۲۲.۵% the amount was under ۱۰, in ۲۷.۵% between ۱۰ and ۱۰۰ in ۲۰.۵% over ۱۰۰ unit/ml anti-HBs was detected. As a matter of fact ۵۲% of the samples were under ۱۰ and ۴۸% contained over ۱۰ unit/ml anti-HBs. Level of antibody decline in boys and girls was equal. One percent of the studied children had anti HBc. Conclusions: Decline in anti-HBs serum level was obvious five years after vaccination. However, this finding dose not either recommend or reject the administration of booster dose of vaccine. This decrease dose not imply potential for infection and it is possible that the subject would be able to produce antibody against the virus in case of exposure. More research including higher sample number is recommended.

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KEY WORDS: Anti HBs , Anti HBc , ۷-۹ year-old children