In this study, comparisons will be made between the treatment group (which will receive pegylated interferon alfa-2b treatment) and the observation group (which will receive no drug treatment or be treated with nucleos(t)ide analogs). The primary objectives are to address the following questions: compare the efficacy evaluation indicators (with clinical cure rate as the primary one) between the pegylated interferon alfa-2b treatment group and the observation group; assess whether pegylated interferon alfa-2b treatment improves the clinical cure rate in patients with chronic hepatitis B virus (HBV) infection aged 3 years and above but under 18 years (adolescents and children); and explore optimized antiviral treatment regimens for adolescents and children with chronic HBV infection. The secondary objectives are to address the following questions: compare the immune response characteristics between adolescents and children with chronic HBV infection who achieved functional cure after pegylated interferon alfa-2b treatment and those who did not; investigate the immune mechanism underlying the achievement of functional cure in adolescents and children with chronic HBV infection treated with pegylated interferon alfa-2b; and identify plasma markers associated with treatment efficacy for predicting therapeutic outcomes.