Predictors of Hepatitis B Surface Antigen Titers two decades after vaccination in a cohort of students and post-graduates of the Medical School at the University of Palermo, Italy

The introduction of a vaccine against hepatitis B virus (HBV) for newborn babies in Italy in 1991, extended to 12-year-old children for the first 12 years of application, has been a major achievement in terms of the prevention of HBV infection. The objective of this study was to analyse the long-term immunogenicity and effectiveness of HBV vaccination among healthcare students with different working seniorities. Materials and method. A cross-sectional observational study of undergraduate and postgraduate students attending the Medical School of the University of Palermo was conducted from January 2014 -July 2016. HBV serum markers were performed with commercial chemiluminescence assays. Categorical variables were analyzed using the chi-square test (Mantel-Haenszel), whereas means were compared by using the Student's t test. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were also calculated by a multivariable logistic regression, using a model constructed to examine predictors of anti-HBs titer above 10 mIU/mL, assumed as protective. Results. Of the 2,114 subjects evaluated -all vaccinated at infancy or at the age of 12 years and were HBsAg/anti-HBc negative -806 (38.1%) had an anti-HBs titre <10 IU/L. The latter were younger, more likely to be attending a healthcare profession school (i.e., nursing and midwifery), than a medical postgraduate level school, and more likely to have been vaccinated in infancy (p <0.001, 95% CI 2. adjusted OR 3.70).