Evaluation of a hepatitis B vaccination program in Chiang Mai, Thailand

• Main Authors: Jutavijittum P., Jiviriyawat Y., Yousukh A., Hayashi S., Toriyama K.
• Format: Article
• Language: English
• Published: 2014
• Online Access: http://www.scopus.com/inward/record.url?eid=2-s2.0-17744393705&partnerID=40&md5=584137aba77dc2755a78c828fabbcafb; http://www.ncbi.nlm.nih.gov/pubmed/15906670; http://cmuir.cmu.ac.th/handle/6653943832/1971
• Institution: Chiang Mai University

Chiang Mai is a province in northern Thailand that started a vaccination program for hepatitis B virus (HBV) infection in 1989. In this paper, we report the long-term efficacy of this program. Of children aged 4-9 years, 65.7% had a complete course and 3.8% had an incomplete vaccination course. Urban schoolchildren had higher percentage of HB vaccination than rural schoolchildren (89.1% vs 46.9% for the complete course, p < 0.001). The overall prevalence rate of HBsAg in Chiang Mai schoolchildren was 1.2%, with no significant differences between gender (p = 0.496) and school areas (p = 0.477). Anti-HBc antibodies were detected in 6.9% of children. Overall, 26.2% of children had protective levels of anti-HBs antibodies (≥ 10.0 m mlU/ml), and 11.2% had low levels of these antibodies (1.0-9.9 mlU/ml). Compared to previous reports, our results show a lower percentage of anti-HBs antibodies, 33.8% of children age 4 years had protective anti-HBs antibodies, dropping to 18.4% by age 9 years. Among those anti-HBs seropositive, 9.1% were anti-HBc positive, indicating a natural infection with HBV. We found a small number of children, despite adequate immunization, developed HBV infection.