Health care workers (HCW) are at increased risk for acquisition of hepatitis B virus (HBV) infection from occupational exposure. This can be prevented by active immunization. We performed a retrospective chart review of HCW who were persistent low (anti-HBs antibody values <100 U/L) or non responders (<10 U/L) after 6 active immunizations and demonstrate successful immunization (anti-HBs ?100 U/l) after a total of 8-14 vaccine doses in 13 such HCW by use of various vaccination schedules. This "proof of principle" should encourage occupational health care providers to convince HCW to accept further vaccine doses until the targeted threshold considered to be the correlate of immunity has been reached. Prospective studies should be performed to determine the optimal schedule of further booster doses for HCW who are persistent non or low responders.