Serological Status of Hepatitis B Virus Infection Among Hill-Tribe Children in Northern Thailand, in 2018

Abstract Thailand has integrated Hepatitis B (HB) vaccine for newborns into the national Expanded Program on Immunization since 1992. The HB vaccination coverage was reported >96% in 2019 but the coverage among inhabitants of remote rural areas, particularly among hill-tribe children, remains unclear. This cross-sectional study aims to investigate the hepatitis B virus (HBV) seroprevalence among hill-tribe children living in 3 different areas in Omkoi District, Chiang Mai province, Thailand during September-November, 2018. Plasma samples were first tested for hepatitis B surface antigen (HBsAg). Sample negative for HBsAg were then tested for antibody to hepatitis B surface antigen (anti-HBs) levels and antibody to hepatitis B core antigen (anti-HBc). A total of 419 hill-tribe children were recruited, their median age was 11 years (interquartile range 9-12 years). Eighteen children (4.3%, 95%CI 2.6-6.7) were HBsAg positive. Among 401 remaining children, 269 had no HBV markers (67.1%, 95%CI 62.3-71.7), 91 (22.7%, 95%CI 18.7-27.1) were positive for anti-HBs only, 23 (5.7%, 95%CI 3.7-8.5) were positive for anti-HBc and anti-HBs, and 18 (4.5%, 95%CI 2.7-7.0) positive for anti-HBc only. The high prevalence of children susceptible to HBV infection and the high proportion of HBV infected children indicate that vaccination strategy needs to be improved in this rural area. Moreover, HBV serologic investigations are necessary in other rural areas to improve HB vaccination coverage. Keywords: Hepatitis B virus; Prevalence; Vaccination; Serological markers; Children; Thailand