A 35-year-old healthcare worker sustains a needlestick injury from a source patient known to be Hepatitis B surface antigen (HBsAg) positive. The healthcare worker completed a full course of Hepatitis B vaccination 5 years ago and had a documented anti-HBs antibody level of 150 mIU/mL one year after completing the course. What is the most appropriate post-exposure prophylaxis (PEP) according to UK Health Security Agency (UKHSA) Green Book guidance?