Inclusion Criteria:  Previously vaccinated with two doses of SARS-CoV-2 vaccines and planning to get booster vaccination. Clinically or pathologically diagnosed with pre-existing liver disease, including: chronic liver diseases, cirrhosis, liver cancer, liver transplant subjects, etc. Understanding and willing to comply with the study procedures and provides written informed consent.  Exclusion Criteria:  Pregnancy or lactation. Active or known history of SARS-CoV-2 infection. Diseases causing immunosuppressive or immunodeficient status or autoimmune diseases. A history of discontinuing anti-HBV agents in recent three months.