RESUMEN
BACKGROUND: Chronic hepatitis-B virus (HBV) infection due to mother-to-child transmission (MTCT) during the perinatal period is an important global health concern. Chile is a low-prevalence country with an increasing migratory inflow from Latin- American countries, with intermediate to high endemic rates of HBV infection, and until 2021, there is no universal maternal screening. This study aimed to evaluate infant outcomes using a risk-based strategy of maternal screening to prevent MTCT of hepatitis B virus (HBV) in a low-prevalence country. METHODS: This prospective study included infants born to HBsAg-positive women detected using a local risk-based strategy. The exposed infants received immunoprophylaxis (IP) and follow-up to evaluate their clinical outcomes and immune responses through post-serological vaccine testing (PSVT) after completing the three- dose schedule of the HBV vaccine. RESULTS: A total of 99 HBsAg-positive mothers were detected. Seventy-six (82%) infants completed the follow-up and had PSVT between 9 and 12 months of age. 55.2% female, the median gestational age was 39 weeks (25-41) and the median birth weight was 3,130g (816-4,400 g). All patients received IP with recombinant HBV vaccine plus hepatitis-B virus immunoglobulin (HBIG) and three doses of the HBV vaccine. There were no cases of HBV infection, and 96% (72) responded to immunization with HBsAg antibodies (anti-HBsAg) >10 UI/ml, with a median level of 799 IU/ml. CONCLUSIONS: A high-risk strategy can be implemented in countries with non-universal screening for VHB. Timely IP plus high-uptake VHB vaccination in infants born to HBsAg-positive mothers was associated with a high immunogenic response and absence of MTCT.