Effectiveness of Stepwise Hepatitis B Revaccination According to Vaccination History in Healthcare Students: a Retrospective Observational Study.

INTRODUCTION: Hepatitis B vaccination and confirmation of adequate immune response are essential for healthcare students at risk of occupational exposure; however, the optimal number of additional doses for individuals who remain anti-hepatitis B surface antigen antibody (anti-HBs)-negative after primary vaccination remains unclear. We conducted a retrospective observational study of medical and dental students enrolled between 2019 and 2023. METHODS: Participants included 1,624 students who received a primary three-dose hepatitis B vaccination series after enrollment and 70 students with a history of hepatitis B vaccination before enrollment who were anti-HBs-negative at enrollment. Students who were anti-HBs-negative after the primary series or at enrollment received one additional dose, followed by two further doses if they remained anti-HBs-negative. RESULTS: Among students who received primary vaccination after enrollment, seroconversion was achieved in 98.1% after the primary series. Of those who remained anti-HBs-negative, 71.0% achieved seroconversion after one additional dose, and 77.8% of the remaining students after two further doses. In contrast, students with pre-enrollment vaccination showed a higher seroconversion rate after one additional dose (88.6%). Anti-HBs antibody titers after the additional dose were significantly higher in students with pre-enrollment vaccination than in those with post-enrollment primary vaccination. CONCLUSIONS: The effectiveness of stepwise hepatitis B revaccination differs according to vaccination history. A single additional dose may be appropriate for students with prior vaccination, whereas planned multiple-dose revaccination may be more effective for those who remain anti-HBs-negative after primary vaccination initiated after enrollment.