PurposePeginterferon alfa-2b (Peg-IFN α-2b) has demonstrated superior efficacy over nucleos(t)ide analogs (NAs) in the treatment of chronic hepatitis B (CHB), particularly among patients with low levels of hepatitis B surface antigen (HBsAg). This study aims to determine whether patients with ultra-low HBsAg levels (< 200 IU/mL) can achieve significantly higher clinical cure rates with abbreviated courses of Peg-IFN α-2b therapy.MethodsIn this retrospective analysis, CHB patients with HBsAg levels below 200 IU/mL were categorized into a Peg-IFN α-2b group and a control group. The Peg-IFN α-2b group received Peg-IFN α-2b for a minimum of 24 weeks, with the possibility of early discontinuation upon achieving HBsAg clearance, and were followed through week 48. The control group remained untreated for hepatitis B virus (HBV), and was observed for 24 weeks. HBsAg clearance rates were compared between groups. Univariate and multivariate logistic regression analyses were employed to identify factors associated with HBsAg clearance .ResultsBy week 24, the HBsAg clearance rate in the Peg-IFN α-2b group was notably 52.1% (38/73), contrasting sharply with the mere 1.3% (1/77) observed in the control group. Within the Peg-IFN α-2b group, a substantial 97.3% (71/73) of patients noted a reduction in HBsAg levels. Besides, the decision to continue or discontinue treatment after the 24-week mark had no significant impact on the HBsAg clearance rate at week 48. Multivariable analysis pinpointed baseline HBsAg levels (OR = 0.984, p = 0.001) and the presence of fatty liver (OR = 5.960, p = 0.033) as independent predictors of HBsAg clearance.ConclusionOur findings confirm that a 24-week course of Peg-IFN α-2b yields robust efficacy in CHB patients with ultra-low HBsAg levels. Prolonging treatment beyond the 24-week threshold is deemed unnecessary. Both baseline HBsAg level and the presence of fatty liver emerged as significant predictors for HBsAg clearance.