This is a randomized, double-blind study to evaluate the antiviral efficacy, safety, and tolerability of TDF versus placebo in adolescents with chronic HBV infection. TDF treatment-naive participants were randomized in a 1:1 ratio to TDF or placebo. After 72 weeks of blinded treatment, participants were to switch to open-label TDF for an additional 2.5 years of treatment, provided that no safety concerns are identified by the Independent Data Monitoring Committee monitoring the study.