Inclusion criteria:

   1. Male or female, age ≥18 years

   2. Chronic hepatitis B diagnosis confirmed by positive HBsAg or HBV DNA or HBeAg or
   documented history of chronic hepatitis B in physician note

   3. Currently maintained on antiviral therapy for at least 48 weeks with any Hepatitis B
   virus(HBV) DNA value at Screening/Baseline and planned to be switched to TAF by their
   physician

   4. Routinely monitored for serum HBV DNA Polymerase chain reaction(PCR), liver chemistry
   including Aspartate aminotransferase (AST )/alanine transaminase(ALT)/total bilirubin,
   renal chemistry including Blood urea nitrogen(BUN)/Creatinine/Carbon dioxide (CO2) by
   their physicians every 3-6 months and a bone density scan at least every 2 years as
   per routine clinical care (one at baseline and one 2 years after switch).

   5. Estimated creatinine clearance > 15 ml/min (using the Cockcroft-Gault method) at
   Screening/Baseline Visit. (Note: multiply estimated rate by 0.85 for women).

   6. Willing and able to provide informed consent

   7. Able to comply with dosing instructions for study drug administration and able to
   complete the study schedule of assessments

Exclusion criteria:

   1. Pregnant women, women who are breastfeeding or who believe they may wish to become
   pregnant during the course of the study

   2. Previous recipient of a liver transplant

   3. Co-infection with human immunodeficiency virus (HIV) or hepatitis C (HCV) or hepatitis
   D (HDV)

   4. Severe or uncontrolled comorbidities

   5. Current or known hepatic decompensation (≤2 years) (e.g ascites, encephalopathy, or
   variceal hemorrhage) with a Child-Pugh score of B or C

   6. Malignancy including liver cancer within 5 years except cancers curable by surgical
   resection (e.g. basal cell skin cancer and squamous cell cancer)

   7. On any of the disallowed concomitant medications listed in the prior and concomitant
   medications list (pg. 11). Subjects on prohibited medications who are otherwise
   eligible will need a wash out period of at least 30 days prior to the
   Screening/Baseline visit.

   8. Males and females of reproductive potential who are unwilling to use "effective"
   protocol-specified method(s) of contraception during the study.

   9. Current substance or alcohol abuse judged by the investigator to potentially interfere
   with subject compliance.

10. Any other clinical conditions that, in the opinion of the Investigator, would make the
   subject unsuitable or unable to comply with any of the study procedures