Persistence of Immunity for Hepatitis B Virus among Heathcare Workers and Italian Medical Students 20 Years after Vaccination

Background: Immunization of healthcare workers (HCWs) and medical students for the hepatitis B virus (HBV) is a crucial part of the hospital infection control programs. The aim of our study was to evaluate the persistence of anti-HBV specific antibodies in HCWs vaccinated during infancy or adolescence. Methods: Medical records of 734 consecutive subjects born after 1980 (481 females, 65.5% and 253 males, 34.5%) who underwent serological testing for anti-hepatitis B surface antibodies (anti-HBs) were evaluated. Results: A non-protective titer (<10 mUI) was found in 88/734 (12.0%) subjects; 84 (47.8%) of them received a booster dose of anti-hepatitis B vaccine and the anti-HBs titer of 58 subjects was measured 1 month after administration. A protective titer (anti-HBs >10 mIU/mL) was observed in almost 90% of subjects receiving the booster dose. Conclusions: A substantial percentage of HCWs had a non-protective anti-HBs titer at the time of the first employment, especially those vaccinated at birth age. However, the response to the booster dose showed that in these subjects, an anti-HBs titer <10 mIU/mL was due to the physiological decline of antibodies over the years. Therefore, primary immunization in childhood is highly effective and provides lasting immunity against HBV infection.