Abstract: 

Background: Hepatitis B vaccine is a key tool in preventing HBV infection. A 3-dose vaccine series induces protective anti-HBs ≥ 10 mIU/mL in over 95% of healthy infants, children, and adolescents.

Objective: This study aimed to assess HB vaccine seroprotection levels and associated factors among vaccinated children in Bahir Dar, northwest Ethiopia.

Methods: A cross-sectional study was conducted in a total of 325 vaccinated children in Bahir Dar from December 2023 to June 2024. Data on sociodemographic characteristics and possible predictors were collected using a structured questionnaire, and serum samples were screened for anti-HBs using sandwich MAGLUMI chemiluminescence immunoassay (CLIA). Data were analyzed using SPSS version 23. Logistic regression was used to check the association between variables.P-value ≤ 0.05 was considered statistically significant.

Results:The HB vaccine seroprotection rate was 55.1% (95% CI; 49.5-60.3). Among seroprotected children, 34.6% were good responders (anti-HBs titer > 100 mIU/mL), and 65.4% were hypo-responders (anti-HBs titer 10-99 mIU/mL). The proportion of children exhibiting seroprotective anti-HBs levels was 135 (59.5%) among those aged 1–4 years, 35 (49.3%) in the 5–9 years group, and 9 (33.3%) among those aged 10–14 years. The age of children (AOR: 3.7; 95% CI: 1.2-11.6; p = 0.023) and the type of health facility where the HB vaccine was administered (AOR: 2.1; 95% CI: 1.1-4.2; p = 0.034) were found to be significantly associated with HB vaccine effectiveness.

Conclusion: Generally, suboptimal seroprotection levels of HB vaccine was reported in this study. The age of children and the type of health facility where the HB vaccine was administered were significantly associated with HB vaccine effectiveness. These findings call for enhanced public health strategies to effectively reduce HBV infection.