Administering an additional hepatitis B vaccination dose after 18 years maintains adequate long-term protection levels in healthcare workers.

HBV (hepatitis B virus) vaccination in first year of life is recommended to prevent infection. Observational studies have suggested that vaccination at birth provides protection for 90% of the population for 30 years. Data on response to booster doses and long-term protection are lacking. We compared HBV antibody levels of healthcare students who were immunized for HBV with a primary series during their first year of life (primary) to students who were immunized with a primary series and received an additional dose at age 18 (boosted) four years earlier. Antibody titres ≥10 mIU/mL were considered adequate. Those that were inadequate received another dose and were reassessed. We assessed 381 students, 80.1% were primary and 19.9% boosted. A significantly higher percentage of students in the boosted group had antibody titre levels ≥10 mIU/mL compared to primary group (88.1% vs. 41.3%,  < .001). Of 179 students in the primary group with inadequate antibody levels, 134 received a booster dose and 126 of them (94%) developed anti-HBs levels ≥10 mIU/mL. Of 9 students with inadequate levels in the boosted group, 8 received another booster dose and all developed adequate levels. Primary vaccination against HBV at birth does not necessarily provide lifelong adequate antibody levels. Boosting at 18 years reinforces antibody levels for at least four more years. Current guidelines recommend testing and boosting all medical personal. Based on our study, it may be prudent to extend this practice to all individuals who are at higher risk.