Persistence of immunity 18–19 years after vaccination against hepatitis B in 2 cohorts of vaccinees primed as infants or as adolescents in Italy oleh Luisa Romanò, Cristina Galli, Catia Tagliacarne, Maria Elena Tosti, Claudio Velati, Laura Fomiatti, Maria Chironna, Rosa Cristina Coppola, Mario Cuccia, Rossana Mangione, Fosca Marrone, Francesco Saverio Negrone, Antonino Parlato, Carla Maria Zotti, Alfonso Mele, Alessandro Remo Zanetti, the Study Group