Interleukin-12 as a Predictor for Unresponsiveness to the Hepatitis B Vaccine: A Novel Cut-Off Point in Children

<b>Background</b>: Despite the widespread implementation of Hepatitis B vaccination, some children fail to develop protective immunity. Thus, identifying markers for vaccine unresponsiveness is crucial for optimizing current strategies. As interleukin-12 (IL-12), a central cytokine in Th 1 immune activation, has shown potential as a predictive biomarker, the aim of this study was to determine its role in the Hepatitis B vaccine response, highlighting novel findings regarding the threshold level of IL-12 in the pediatric population in doing so. <b>Methods</b>: A cross-sectional study was conducted on a community in Bandung City. The subjects were 7-12-month-old babies who had completed primary Hepatitis B vaccination (0, 2, 3, and 4 months of age). Blood tests for anti-HB examination were performed with a Chemiluminescent Microparticle Immunoassay (CMIA) to determine the response and non-response groups, and an Enzyme Immunosorbent Assay (ELISA) was used for IL-12 detection. Data were analyzed using the Kruskal-Wallis test, Chi-square test, Spearman Correlation, and Receiver Operating Characteristics. Statistical analysis was conducted with SPSS version 18.0. <b>Results</b>: The results of this study indicate that 4.5% of the subjects were unresponsive to the Hepatitis B vaccine. The most important finding was a significant correlation between IL-12 and the presence of anti-HB titers in the responsive and non-responsive groups (<i>p</i> = 0.016). The Receiver Operating Characteristics (ROC) curve for IL-12 identified a cut-off point of ≥10.65 pg/mL (>100 mIU/mL in anti-HBs), with a sensitivity of 64.23%, specificity of 68.75%, and accuracy of 65.2%. <b>Conclusions</b>: Interleukin-12 can be considered as an early candidate biomarker for responsiveness to the Hepatitis B vaccine in children.