Anti-HBs Concentrations and Post-Booster Serological Response Among Romanian Dental Students

Background/Objectives: Hepatitis B virus (HBV) infection remains an important occupational concern for healthcare students exposed to blood and body fluids. This study aimed to characterize hepatitis B surface antibody (anti-HBs) concentrations according to reported vaccination history among Romanian dental students and to assess the early serological response to a booster dose in participants with baseline anti-HBs concentrations < 10 mIU/mL who completed follow-up. Methods: This cross-sectional study with a prospective follow-up component included 155 dental students. HBsAg and quantitative anti-HBs were assessed alongside demographic characteristics and self-reported vaccination history. Anti-HBs concentrations were categorized as <10, 10–100, and >100 mIU/mL. The association between vaccination history and anti-HBs category was evaluated using the Fisher–Freeman–Halton test with Monte Carlo estimation. An exploratory multivariable logistic regression examined the association of recent immunization, age, and sex with anti-HBs concentrations ≥ 10 mIU/mL. Results: At baseline, 130/155 participants (83.9%; 95% CI, 77.3–88.8%) had anti-HBs < 10 mIU/mL, whereas 25/155 (16.1%; 95% CI, 11.2–22.7%) had concentrations ≥ 10 mIU/mL. Vaccination history was significantly associated with anti-HBs category (Monte Carlo p < 0.001; Pearson χ2(12) = 96.865; Cramer’s V = 0.559). In the restricted regression sample (n = 111; 21 outcomes), recent immunization was strongly associated with anti-HBs ≥ 10 mIU/mL after adjustment for age and sex (aOR, 28.45; 95% CI, 7.52–107.61; p = 8.09 × 10−7), while age and sex were not significantly associated with the outcome. Of the 130 participants with baseline anti-HBs < 10 mIU/mL, 12 received a booster dose and completed repeat testing approximately one month later; all 12 achieved anti-HBs concentrations > 100 mIU/mL. Conclusions: Most participants had anti-HBs concentrations below the conventional protective threshold, particularly in the absence of recent vaccination. The uniform post-booster response among participants who completed follow-up is consistent with preserved vaccine-induced immune memory despite low baseline antibody concentrations. These findings highlight the importance of documented HBV vaccination and appropriate assessment of hepatitis B immunity among healthcare students at occupational risk.