Hepatitis B vaccine-induced immunity among hill tribe and stateless children in northern Thailand

The aim of this study was to determine the difference in seroprotection between fully and partially vaccinated hill tribe and stateless children aged five years in northern Thailand along with the factors associated with the absence of anti-HBs in these children since vaccine implementation began in 1992. A case–control study was conducted to collect information from hill tribe and stateless individuals living in villages in Mae Fah Luang District, Chiang Rai Province. Children with no prior immunization, delayed immunization, or incomplete hepatitis B vaccination were included. Children who were completely vaccinated were included as controls. A questionnaire was distributed and 3 mL blood samples were collected for the qualitative and quantitative detection of hepatitis B biomarkers. Logistic regression was applied to detect factors associated with the absence of anti-HBs. A total of 188 cases and 188 controls were included in the study; 54% were male, and 54.3% belonged to the Akha group. The overall prevalence of anti-HBs was 59.3%; 55.3% of anti-HBs was detected in children with complete vaccination (with 2 children positive for anti-HBc), and 55.3% was detected in children with incomplete vaccination. Children whose birth weight was <2500 g (AOR = 3.52; 95% CI = 1.39–9.12), whose mother belonged to the Yao group (AOR = 16.90; 95% CI = 2.00–142.57), whose mother practiced Christianity (AOR = 2.30; 95% CI = 1.18–4.46), and whose father was aged 30–39 years (AOR = 2.20; 95% CI = 1.01–4.80) were more likely to exhibit an absence of anti-HBs. The hepatitis B vaccine-induced immune response rate among hill tribe and stateless children remains undesirable, and an effective assessment program is needed to monitor this issue.