Evaluation of a hepatitis B vaccination program in Chiang Mai, Thailand.
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 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.
Jutavijittum
Prapan
P
Department of Pathology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand. pjutavij@mail.med.cmu.ac.th
Jiviriyawat
Yupa
Y
Yousukh
Amnat
A
Hayashi
Shigeki
S
Toriyama
Kan
K
D000914:Antibodies, Viral / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D019353:Endemic Diseases / Q000517:prevention & control; D005260:Female; D006509:Hepatitis B / Q000453:epidemiology / Q000517:prevention & control*; D017325:Hepatitis B Vaccines / Q000600:supply & distribution; D006515:Hepatitis B virus / Q000276:immunology*; D006801:Humans; D017589:Immunization Programs / Q000592:standards* / Q000706:statistics & numerical data; D008297:Male; D015995:Prevalence; D015397:Program Evaluation; D012423:Rural Health; D013785:Thailand / Q000453:epidemiology; D016896:Treatment Outcome; D014504:Urban Health
D000914:Antibodies, Viral; D017325:Hepatitis B Vaccines